Brown Spots & Yellowing of fan leaves @ 4 wks flower.

Hello everyone! This is my second closet grow, and after a successful first grow I am stoked to harvest again. I have 6 plants in Fox Farm soil, under a 400w hps, light at 12/12, circulation fan, temp stays between 72-76 degrees, humidity stays around 40%, watered with Nestle Pure H20 (which is supposed to be a pH of 5.5), and they are fed Tiger Bloom, and Big Bloom Fox Farm nutes every other watering (once/wk).

All of the plants are big, green and healthy except for one, Wild Purple, which is turning a light green/yellow color and has developed brown spots on the fan leafs, and some of the top leaves. The buds that are forming are beautiful, and the plant doesn't appear to be croaking.. but I simply don't know what the brown spots are, and don't want to let it get any worse. I've checked for spider mites/pests/bugs- none. I do feed a lighter dose of nutes, because I tend to err on the side of caution. I checked the soil pH today and it was 7.0, which I know is slightly high.

Any advice would be appreciated. I'm leaning on feeding it some Cal-Mag to see if it's a Mg deficiency, but it is such a beautiful plant, I really don't want to use it as my test subject. Thanks in advance, and sorry about the crappy pics!!!!

Happy Growing :jointsmile:

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Ingoing water should be between 6.3 and 6.8 ph. In buffered, peat-based soils, going outside that range creates a nutrient lockout condition. HAve you read the info Fox Farms provides in their Weekly Feeding Schedule? (for soil)
I'd lean twords calcium def though. CalMag or unsulphered molasses should help. Find and read the "Epsom salt is not a miracle cure" thread. It's around here somewhere...

Your ph numbers don't sound right. What is your water ph? (test it and see)
What are you using to test ingoing and runoff ph?

Well, I tested the pH of the soil again, and it's 7.0 on the dot. I also tested the water that I feed it, and it has a pH of 6.6. So both are a little high. I typically do not test the pH of the run off, but will start at the the next feeding. I have looked at the FF soil feed schedule, but only for feeding instructions.

If this were a pH problem, why would it be affecting only one plant? Does pH affect each strain differently? Also, what should I do to safely lower the pH?

In addition, should I go ahead and give the Cal-Mag?

Any and all help is much appreciated. Thank you.

I am having this same problem in the flowering cycle also. I can tell you that it did not happen because of a change it light cycle though which im sure you know but mine started turning brown on my fan leaves about 3 days before i switched to the 12/12 so I know its not that. This is my first grow that ive done with Canni but ive done some pretty amazing things with veggies like cross breeding a strawberry plant and cayan peppers but this is a whole new set of probs. I dont have the ph kit (yes i know I need one but I am disabled and havnt worked for 3 years so i dont have the money) Ive got a website that I know of that might help you. Ill link it up here for ya. Its got pics of all, well most of the probs that these plants go through. If I remember correctly the closest pic that looks like my prob is low Mg. Do you have anyway of testing that? Some people say that low mag can be fixed with epsom salt in the h2o but some are very against it so I guess thats up to you to decide on. If you figure it out, post it up here please id like to know before its ruined.
My canni is a Mango, she is a sensi clone, 16in now and was moved into 12/12 5 days ago. It may not be related but take a good look in the soil and around the area for little worms. Ive found a couple of them in my res tank and the soil but nobody seems to know what they are. Ill attach a pic too.
Marijuana Plants Problems - Yellow Leaves, brown spots, nutrient shortage etc.

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Originally Posted by greenthmb

Hello everyone! This is my second closet grow, and after a successful first grow I am stoked to harvest again. I have 6 plants in Fox Farm soil, under a 400w hps, light at 12/12, circulation fan, temp stays between 72-76 degrees, humidity stays around 40%, watered with Nestle Pure H20 (which is supposed to be a pH of 5.5), and they are fed Tiger Bloom, and Big Bloom Fox Farm nutes every other watering (once/wk).

All of the plants are big, green and healthy except for one, Wild Purple, which is turning a light green/yellow color and has developed brown spots on the fan leafs, and some of the top leaves. The buds that are forming are beautiful, and the plant doesn't appear to be croaking.. but I simply don't know what the brown spots are, and don't want to let it get any worse. I've checked for spider mites/pests/bugs- none. I do feed a lighter dose of nutes, because I tend to err on the side of caution. I checked the soil pH today and it was 7.0, which I know is slightly high.

Any advice would be appreciated. I'm leaning on feeding it some Cal-Mag to see if it's a Mg deficiency, but it is such a beautiful plant, I really don't want to use it as my test subject. Thanks in advance, and sorry about the crappy pics!!!!

Happy Growing :jointsmile:

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Looks like a sour gummi worm...Sorry, I know your trying to be serious...you got any kids runnin around loose in the grow room? Worms in the res??? I dunno about that...Something I've noticed and been doing is still giving them veggin nutes for the first few weeks of flowering...seems to keep them greening longer into flowering, then as the buds start forming I switch to flowering stuff....and Molasses! It's cheap, organic, and loaded with goodness! See and read Sticky! Fan leaves are going to yellow and fall off during flowering...it just happens. I don't worry too much about it as long as the plant as a whole looks ok, and things are still moving towards a finish.

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Originally Posted by TANKJR

Looks like a sour gummi worm...Sorry, I know your trying to be serious...you got any kids runnin around loose in the grow room? Worms in the res??? I dunno about that...Something I've noticed and been doing is still giving them veggin nutes for the first few weeks of flowering...seems to keep them greening longer into flowering, then as the buds start forming I switch to flowering stuff....and Molasses! It's cheap, organic, and loaded with goodness! See and read Sticky! Fan leaves are going to yellow and fall off during flowering...it just happens. I don't worry too much about it as long as the plant as a whole looks ok, and things are still moving towards a finish.

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[align=center]that is a gummi worm I WOULD NOT EAT! Id rather not say about the kid, it may sound bad when its not.( i can say that there is no smoking in the house or around the kid though) Were you thinkin like ringworm, tapeworm that kinda thing? I guess I hadnt thought of that but our kids clean. Her half sister did have ringworm a while back when she stayed here but she wasnt around the plant.
I cant seem to find an actual picture of what a ringworm looks like. We'll here I am rambling about this and I dont even know if thats what u meant.
I have a good pic of what is happening to mine. Ill attach it. Its pretty bad but only on a 3 or 4 leaves. Check it out. What do u think?[/align]

Just to inform you, Ringworm is not an actual worm, it is a fungal infection, therefore ringworm can not be found as a worm, and ringworm, or intestinal parasites, can not be transferred to a plant.

I personally have not seen any worms around the plant, or in the soil.

I have purchased Cal-Mag by Botanicare, and gave my plant a dose. Hopefully I will see an improvement soon. I also purchased a new pH test kit (simple, add drops kit) and tested the run off water and it had a pH of 5.0?!?!?!?! Which doesn't seem to make sense, being that the H2O I am feeding has a pH of 6.5-6.6, and my soil pH meter (which I question the accuracy of) reads 7.0. Ooooh dear, I am confused now...

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Originally Posted by greenthmb

Just to inform you, Ringworm is not an actual worm, it is a fungal infection, therefore ringworm can not be found as a worm, and ringworm, or intestinal parasites, can not be transferred to a plant.

I personally have not seen any worms around the plant, or in the soil.

I have purchased Cal-Mag by Botanicare, and gave my plant a dose. Hopefully I will see an improvement soon. I also purchased a new pH test kit (simple, add drops kit) and tested the run off water and it had a pH of 5.0?!?!?!?! Which doesn't seem to make sense, being that the H2O I am feeding has a pH of 6.5-6.6, and my soil pH meter (which I question the accuracy of) reads 7.0. Ooooh dear, I am confused now...

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Ya sorry about changing the topic but take a look at the pics i posted with my last post. Is that what you are talking about with the brown spots on the leaves? I would still take input on what people think that worm in my pic is. You are correct about the fungus of ringworm.

That is what mine look like, but the brown spots are smaller and more circular... and the leaves have turned more yellow than yours. Now that I've tested the pH of the water I feed which is 6.6, and the run off, which is 5.0, I am really confused.. Something in the soil is massively lowering my pH..

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Originally Posted by greenthmb

I also purchased a new pH test kit (simple, add drops kit) and tested the run off water and it had a pH of 5.0?!?!?!?! Which doesn't seem to make sense, being that the H2O I am feeding has a pH of 6.5-6.6, and my soil pH meter (which I question the accuracy of) reads 7.0. Ooooh dear, I am confused now...

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I'm not. Tiz why I asked those specific questions. :thumbsup:
Soil probes are notoriously inaccurate, likely your soil is buffered fine, and if your ingoing (plain) water is 6.5ish, that's fine too.

Yellowing with brown starting at tips and progressing twords the petiole (leaf stem) is overwatering or a drainage issue.

Yellowing and dying-off of fans is either insufficient light or a natural aging of the maturing plant's fan leaves as the plant 'borrows' it's nutrients and such.

Yellowing with blotches is usually a calcium deficiency. In your case, this is the likely issue, as different plants have different calcium needs and tollerances. Add it to the water per instructions.
Old leaves are old news, so don't expect to see leaves miraculously recover. But the other parts of the plant should show improvement after a couple of applications.