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.