Pale and brittle leaves on slow growing seedlings

[Reve]

Hey everyone!

This is my second grow. The first grow went surprisingly well without too many complications. However these current seedlings have already been out of the ground well over 2 weeks but the problem is that the bottom leaves are starting to turn very pale, without any spots, after which they seem to get brittle and die... I also feel like the seedlings are not growing as fast as they should, considering they are sativa's and well over 2 weeks above ground

On the pictures the ground seems quite wet, but this is because I've watered yesterday and reflections make it seem like it's alot worse, but its not.

I should also note that I thought I discovered the problem 2-3 days ago as I had a fan blowing over the seedlings which caused the soil to be bone dry in about 2 days. So I thought maybe the seedlings were being dried out because of the fan, or got way too much water flowing through them too fast because of this fan drying it out, so I've decided to turn that fan off, at least until they're quite a bit bigger to be sure they can manage it. Maybe this did actually do the trick, but I haven't been able to see progression, and it looks like some of the newer leaves are starting to turn yellow now, but maybe it just needs some time to readjust, I don't know. But maybe I'm missing something else so that's why I'm asking

Anyways, some more info about the grow(& room):

Room is 3ft x 1.5ft x 3ft, properly ventilated (currently about 65cfm, increased to like 90cfm in flower)
I'm growing them (for the first time, previous grow was only cfl) under a TopLED Reflector 96x3w on Veg mode
Temperature when lights on is generally between 24 and 30 degrees celcius (75 to 86 fahrenheit), depending on the weather. When lights are off, I'd say the temperature is between 15 and 20 degrees celcius (60 and 70 fahrenheit).
Humidity is about 60% when lights are just turned on, at the time they're about to go off, the humidity usually is about 40%.
The water here has a quite high PH (about 8) which I bring down to about 6 / 6.5 using PH- (bloom though, hope that doesn't matter?)
Soil is coco and I'm not using any nutrients yet
I usually water when the cups are feeling very light, and I'm quite sure I'm not overwatering them anyways
All 5 seedlings are Kali Mist

Here are pictures to see what I'm talking about:

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I hope someone's got enough info to help me ^^,
Thanks!

 

[jamthe3]

Coco is great to grow in but is notorious for needing a cal/mag supplement. Also, you don't want to dry all the way out really between waterings; its a little bit different than soil. Ph for veg needs to be more like 5.8-6.1 tops and I usually in bloom will float as high as 6.25 sometimes...any higher doesn't really work to well so I'd work on getting that 6.5 down quite a bit.

 

[Reve]

Thanks for the reply @jamthe3, I'm quite new to this and didn't think I had to be that precise about it, but I'll watch out for that better in the future. Anyways, after your reply it seemed to me that you were sure this was a ph problem leading to deficiencies, so I went looking for some of those that matched mine until I found this info about nitrogen deficiency which seems to be describing my problem exactly:

So I've just given some water to adjust the ground to be ~6 ph, and added a little bit of growing nutrients containing nitrogen among others. I suspect this will be enough to revive them, so thanks!

 

[jamthe3]

This is a nice post from one of the staff writers which might help also, coco's considered hydro: ph balance

 

[swazi]

If your coco has no nutrients, adding a small amount should bring them back around. Sometimes over feeding can present in similar ways to not enough, and seedlings are pretty sensitive to that as well. If adding nutes doesn't do the trick, you might try flushing one or two of those little fellers with water (let it run freely out the bottom) to see if it'll help. Good luck - Kali Mist is a really nice sativa!

 

[Reve]

Thanks guys, just a little update, they started to grow better immediately, I saw a real difference in 2 days already, but I think my problem may be a bit different then I originally thought.

While I was looking at the seedlings I noticed that the getting pale was continuing on the newer leaves but that the color wasn't actually yellow, but almost white...like losing its color. So instead of pale and yellow, I went googling for white leaves. After looking through a few posts etc, I found some people talking about light burns with led etc. and as I've stated I'm using a 96x3w Reflector led panel on veg mode (for the first time, too) and didn't realize that this must be handled a bit differently as opposed to CFL lights which can be put pretty much up until an inch or two on the leaves. I actually had my led panel 5 inches above the seedlings, so I'm pretty certain that's the cause of the leaves to get this pale, and it also seems obvious as older leaves are effected just because they have been receiving the light for a longer time.

I've moved the light up as far as I could for now, which is about 13 inches above the seedlings, and I'm hoping that's enough for now. As for the brittle tips, this may have been caused by too little nutes, wrong ph, too much wind, or maybe simply heat stress or a little bit too dry air. I've taken action against all of these the best I could. I've added a little bit of growing nutrients to the better ph'd water, created a better air intake while not having the fan blow directly on the seedlings and added a humidifier to try to keep the humidity around 60-70%.

I hope these measures will do it, and I suspect they will for most of them, however I do doubt whether the worst looking one (with the most brittle leave tips) is gonna make it through. The others seem to be strong and handle things pretty well, aside from going pale