brown spots on leaves, can't find solution please help

Hi I'm new on here and need a bit of help. i have a few plants some of which have brown spots and the tips get crispy. They are in a potting/cutting soil, perlite and vermiculite mix and am feeding them with biobizz. They are about 5 weeks old and are clones. Only giving 2ml nutes per 1litre which is half of what it says on the bottle. just got a ph test kit and the water and nute mix seems to be fine, well it is around the 6 mark, which from what i've read seems healthy enough. My test kit only tests between 6 and 7.5 as i wanted one quick so got one from the pet shop for aquariums. I don't have a soil tester though so don't know if thats ok, but its not affecting all the plants. I also have some seedlings in rockwool that are about 3-4 weeks old and they seem to be doing just fine, although they're getting diff nutes but ph is fine there too.

I have done a few grows which have been successful and didn't really have any probs till now. I have read a few things and sites about deficiencies and ph probs but can't really find one that matches my prob. On one site it looked like a calcium def caused by ph prob but since ph seems ok could it still be calcium def? I water when they need it, around every 2-3 days with nutes, could i be over nuting them even though the other plants are ok? the plants also seem to be slowing in growth, 2 or 3 of them are getting these spots quite bad and the leaves are looking well crispy.

Does anyone have any ideas on what i could try? thought about flushing them but i'm a bit dubious incase they get over wet if you know what i mean, how would i go about it properly? i haven't needed to flush before.

Also, do you need a soil ph tester to test the soil ph or does the runoff give an accurate enough reading? and if so how do you correct it if it is off? Sorry if this is a bit of a babble but don't want to lost my babies and getting desperate!!
I will try to get pics on tomorrow as i only have a cam on my phone and it needs charged the now.
Please let me know if you need more info to help me, thanks:

Runoff is accurate enough.
pH 6 is too low, and if you are at the bottom of the range that your strip says, how do yo uknow it's not actually lower? Get it up between 6.5 and 6.8.

If you are using enough perlite or vermiculite, flushing should not be a problem. Use water that is at pH 7 since your pH is TOO low atm. Flush with 3x the volume of the soil. This sounds like a problem of lock out and once you get your soil pH up to the 'good' range you will see improvement.

thanks for that, just want to check that i'm going to do this right. I only mix up the nutrient with the water as i need it, so should i add ph up to my tank of water which sits at ph7 from the tap, so that when i add my nutrient it should be at about 6.5-6.8, as when i add the nutrient that is when it lowers to around the 6 or lower mark. If so what should i make the water ph, about 7.8 or so to allow for the lowering of the nutrient? I will have to get another ph tester with a bigger range, but once i've flushed how long do i wait before adding more nutes, just once it needs a drink again? Hope i don't sound too stupid, thanks

Don't pre-mix nutes and let them sit around. Tanks are for hydro grows; for soil grows, mix up just what you need, when you need it.

Mix the fertilizer first, then test, and adjust as necessary.

sorry i've maybe not explained properly, i only let my water sit so i can heat and aeriate it, i only add nutes when i need to, ie i mix up two litres of water with nutes at a time as that is what my watering can thing takes. I've got about 80 litres of water in my tank, and i take out two litres and then add nutes, reason i was asking if i should make ph of water in my tank higher is because the ph up and down that i got states 2.5ml per 90 litres, and not sure how to work it out for such a small amount of water. so if i was adding the ph up to my 2litre water can with nutes, not sure how much ph up i would add. sorry if i'm being a pain!!

I adjust my pH dropwise and re-test until it is correct, if I'm adjusting it at all.

That 2.5mL/90L is for a specific increase... if you need to increase LESS, then you use less, etc.

Unless your tap water is really bad, just use room temp water right out of the tap, then add nutes, then test pH, and if it is off, adjust accordingly. I think you are adding an extra step, if I am undesrtanding you correctly.

ok thanks for that i'll give it a go with a flush and then new ph levels with nutes and hopefully it will sort things out, cheers

hi just wanted to check, once i've flushed with plain water, should i flush with weak nute mix with ph adjusted when they are ready for a drink again? just that i saw it in another post, but unsure if it applies to my problem, cheers

Quote:

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Originally Posted by bonclyde

hi just wanted to check, once i've flushed with plain water, should i flush with weak nute mix with ph adjusted when they are ready for a drink again? just that i saw it in another post, but unsure if it applies to my problem, cheers

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yes do that, it actually applies perfectly to your problem.

cheers for the help by the way, theres new growth on the ones i flushed first already which i aint seen for a wee while, so lookin good, doin others now, ure a star ta!

[btw, stinky's the best, eh?!]

...what size pots are yer girls in right now, and what size do you eventually get 'em into before harvest..?

{inquiring minds and all that sorta...}