Having some troubles with plants leaves

[Cunjo420]

Hello,
Here is me with new problems...nothing new
First the healthiest plant has some yellowish dot as you can see on picture now Im not sure is that sun burn but it doesnt look too bad

Second plant I have problem with, she is growing in height while stems has black spots, which is wierd for me why is stem blackish.. she grows normally but not with too much foliage

Third plant I have problem with, new growth on top started curling inwards, like really twisted in, I topped her because that new growth was awfull looking but also it was time I wanted to top that plant, but you can see few leaves on top(bigger ones) still twisted a bit.

Pictures might be randomly placed,
I am barelly feeding fertilizer every few days so they are mostly feeding on water, they all grow side by side, one with blackish stem grows in different soil so even that might be problem. But they mostly have same treatment.
Hope anyone can recognize problem.
Thank you

[UndergroundFarmer]

The stems are showing some purpling which is normal enough for some varieties. In others, it can mean a phosphorus deficiency. Either way, it isn't all that serious. You've got tacoing happening up top which is likely heat stress. The yellow spot is probably where a drop of nutes splashed on that leaf during feeding. Try searching the guides here with the search terms "red stems" and "tacoing" for more help. I haven't grown in soil yet so someone more qualified can advise you there.

[Cunjo420]

well anyways, your reply helped, thanks. Now that I think off, there is even possibility for heat stress since floor where I place the plants ussualy gets very hot from sun.