Plant stopped growing

Just mine are not yellow. I just been feeding distilled water with PH down. Nuts will be here Tuesday.

Hmm, I'm having the same issue. I planted 2 purple Kush's and 1 is half the size. Could it be a dwarf? and would it matter?

You mentioned you weren't checking your pH until 4 weeks that's a big no no and probably why you see defeciencys now. I see defeciencys in zinc, iron, sulfur and maybe potassium. You are also not listing any nutrients, you must be feeding with something? Make sure you add some calmag to whatever your feeding, use plain water every 2 or 3 feeds, check ph every time, check ph and tds runoff. 🌱👍

As far as the differences, can be genetic diversity, but the issues are defintely having some impact too. First, make sure pH is good and consider recent behaviour fertilizaing before acting on anything i say. there's a multitude of information you have that i don't, and it is unreasonable to expect you to provide all of it. Light burn starts out a bit like that. This is a possibility if you have a strong light and the plant is much taller -- try lifting shorter plant with some books or whatever underneath to even out canopy then adjust light. It really does look like that, i've seen it before from putting an indoor plany out in sun during a power outage... stupid, stupid, stupid me. K and P Toxicities have ineterveinal chlorosis at the top. These also cause Mg and Ca deficiencies, so look for hints of those related symtpoms to help confirm. Also, using coco, so if not washed/buffered well it can easily cause a k-toxicity. This is a real possibility too, but you could rule it out if oyu prepared it or you know the quality of the product you bought.. jsut down' say 5kg brick by mother earth, because that'll kill your plants, lol. As i write this, i'd bet it's the light due to significant heigh difference. 20cm is nearly 12 inches, and that's 1/4th the strength just 12 inches further? or is 1/2? either way, it is a drastic difference in intensity.

Have you been checking the pH of your water and soil? seems like some sort of Mag deficiency. I'd suggest checking it if you haven't.. and possibly start a cal-mag feeding if you haven't already. Hope this helps!