Bunch of defs on my plants, why?

Hey guys,
So I'm currently growing 3 autoflowering feminized Northern Lights (from nirvana), it's my 1st grow and as for today they're at week 6 from seedlings.
The problem is each plant has it's own def and I can't figure out why is it happening (considering the fact they all get the same ferts and water).
Here are some photos of each plant:




The 1st one is burned all over his leaves, and 2nd has this discoloration at the outer part of his leaves, and the 3rd one is getting his edges burned for some reason.

a few things I have to mention:
1) Due to budget I only use 1 fert - BioGrow, at a 4ml/liter ratio.
2) They are about 40 cm away from the lights - and I use CFL (150w 2700k + 100w 6400k).
3) I started to use a/c water + always make sure to balance pH level to 6.0-7.0.

Please help me get my babies healthy :'(

Thanks!

try some epsom salt, and some garden calcium from wallyworld, 5$
1tsp of e.s
1/2 tsp of calcium
mix with 1gal

Their starving!!! Feed them! At that stage, they are at their peak of growth and require full strength, short changing them now will effect your yield. Using epsoms will green them up a little, but they look like they require a stronger solution not just mag. Do you know the ppm and ph of what your feeding? This is not the time to cheap out if you can because a little extra cash spent right now goes directly to your yield.

it looks like burn aswell as some nute issues to me

Picture 1 shows a plant that looks very much like a potassium shortage. The rest it is hard to tell what is wrong. K deficiencies can be helped by using bloom foods as they usually have a high K ratio. Liquefied kelp and wood ash are other sources. Do you add Calmag to your nutes? I would recommend starting if you don't, because at around 6 weeks deficiencies in calcium and or magnesium usually start showing up around then in soil grows. Peace

How hot was your grow box/room/area 7-10 days ago ?
Heat stress looks like cal/mag issue and N deficient...
Be careful of the heat...
There is hot spots in your grow...if temp gauge says: 84f.... it's probably 87-88 somewhere in the grow...
88 f will cook the plant, and then, death, a slow ugly starvation...
Good Luck...

I keep my temp at a steady 77-79 F so I don't think that's the issue.
I don't use Cal-Mag nor any other nut besides BioGrow. Should I buy Bio-Bloom and Bio-Heaven? They don't sell CalMag at my local hydro-shop, nor epsom salts of garden calcium - What should I do?

And you guys suggested alot of nuts, are you sure they won't kill the plants if I'll just go throw all these ferts at them? Do you think it's 100% mag-cal def?