yellowing at tips then drying up

hello im trying to help a freind out whos having problems growing. hes growing in coco soil using coco a and b, hes growing in a tent with 2 400w lamps with the temp at 26C with the lights on 18hrs a day, he used 30ml of coco a and b and 5 ml of bio - stimulant and and the plant started to yellow at the tips so hes been flushing it out for the last 2 weeks with ph water at 6.0 the new shoots are coming green then still yellowing at the tips some curling up then drying n falling of. can anyone please help hes gave 1 feed of 10ml coco a and b since. thank you

Nice pic's that help's alot.

My first guess is going to be over-watering.You want the first inch or 2 of soil to be dry before re-watering.What over-watering causes is root rot,weak root's=weak plant.

Dive:stoned:

i don't have any experience with coco, but i've read it likes a little higher pH than 6.0. i've read anywhere from 6.3-7.0. it's pH neutral, so 6.5 should be good?


-shake

thanks i will tell him about teh watering we heard that he had gave them too much feed and that they need to be flushed out, hes been doing that over 2 weeks now with 1 feed of 10mill a and b . there 7 week old now and the growths been stunted, any more advice would help as he does'nt want to lose the plants.

thats how mine went, growing in DWC. tURNED OUT TO BE pythium. Check my threads.

Your 'friends' plants look generally very healthy so I doubt it's over watering or root rot in this case. Looked like a deficiency of some sort so I did a couple minutes research. Sounds like coco has a tendency to absorb calcium. Apparently you need to supplement. I'd recommend trying that cal-mag stuff and check the pH of the run off just to be sure. Get them back on their normal strength feed too, otherwise you'll probably compound the problem. You're better off with a tiny bit of tip burn than under feeding from my experience.
Is using Coco the new fad? Better off sticking with rock solid proven mediums like a perlite/vermiculite combination and normal nutes if you ask me.

Nice serated leaf edges. What's the strain?

See links I found re: coco and calcium/mg.

What's the issue with calcium/magnesium? - International Cannagraphic Magazine Forums

CN: Cannabis Community > epsom salts,canna coco nutes,coco perlite..hhhmmmm

First Coco Grow Going Downhill - Grasscity.com Forums

its blueberry he says! i will tell him to put more cal mag in, and when he does how much should he put in with each feed???

im going to oer when he finished work today and check the run off i'll report back later...cheers guys.

did your friend just water in those pictures? it looks like they are standing in water in the first two pics. those drip pans should be removed.


-shake

hes a bit of a newbie!! he feeds the plants from the bottom thats why theres water in the bottom of the trays. we did a run off check and he put 7.2 ph water in and it came out 6.5 he hasnt fed in a while, he wants to know what cal-mag supplent he should get. the EC of the water was 0.6 before and the run of was 2.0 if that matters, i think he needs help and any advice or tips whats he doing wrong would help.

Look out, you gave them about 3 times the normal dosage. As for testing coco's ph I'll post a new thread shortly with the correct method.

tell him to feed them from the top, and to let the water run out of the bottom. leave the saucer off altogether. this will also help the roots get oxygen.

what's the green stuff all over the top of the coco?


-shake

ie told him to feed from the top i dont know why he does it. i havent got a clue what that green stuff is i thought the same. all i know he grows in coco soil uses a + b which we think he gave too much of and he gave a feed of bio - stimulant, flushed out for over 2 week now and has gave 1 little feed. but the tops leafs look good then go they same way as the other leafs. the process starts at the tips then gradually takes the whole leaf curling up then dying. he has this halo foiler spray what has magnesium supplement in it but hasnt used. its his 1st time using coco products too, which was a bad mistake, when i start ill make sure to have a good read up on this forum 1st.

and plus theres hardly any roots coming out of the bottom of the pot.

wow... that almost looks like ALOT of algae or forest moss but... i can't possibly picture how that much could grow that quickly there... or if it could at all... i know algae can grow on perlite, but its not like there is a ton of perlite there

we have repotted 5 of the plants in his last bit of coco soil and we have fed the plants 300ml each with 15ml of A and 15 mil of B and gave it 2.5ml of bio stimulant to 5 litre of water, the ph of it was 6.5. we fed the 300ml round the base of the plant but it looks like we gave it nothing as there 10litre pots is this ok???

also when we repotted them the roots looked fine and the soil was wet as he was feeding the plants 1 litre of water every other day thats why there was so much water at the bottom of the plants, some of the leaves look like venus fly traps as they've curled up and the leaves look droopy and stems or fairly droppy aswell is this a sign of over watering??

I don;t know anything about coca soil... but 300ml of water to a plant occupying a 10 litre pot does not sound like a lot to me...

again... not knowing coca soil, watering every other day also sounds like alot to me, but that also depends on the size of the plants, strain, ambient heat, etc. that might be perfectly normal for your situation.

from what you describe (leaves curling upwards from the sides), is not a sign of over-watering i believe... taking a look at this page: Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos the symptom of those leaves could be a magnesium deficiency... but you didn;t mention yellowing of the leaves, so... that also doesn;t really fit, but i don;t know what else would cause the leaves to curl in that pattern... hopefully somebody with some more knowledge will chime in for ya

take my comments with a grain of salt though - i am pretty far from being a cannabis growing troubleshooting expert