Darkened/curled leaves

Hey guys, my 3 plants are 4 weeks old, and 2 of them (the more developed ones) now have darkened and curled leaves:

1) Pics:


2) Growing indoors
3) Watering schedule: every other day
4) Growing Medium: vermicast
5) What stage of growth: 4 weeks old - 18hs light - 6hs dark schedule

Any tips on what could be happening with these girls?

Thanks!

Vermicast..

For 4 weeks they are really small

if you can get foxfarm light warrior soil or roots, get a bag and put them in it, preferably in 3 gallon containers. let them about 12 inches tall, then transplant into ff ocean forest soil, lots of it to last the grow. just add water. don't pH anything. don't add anything. it's that simple.

That soil ( medium ) looks compacted .

Very far behind for a month old. I’d start over with a different medium.

Thank you for the suggestions, yes it does look very small for 4 weeks, it's my first try..
So you suggest transplanting in a well prepared and less compacted soil, I'll look into that..
@polishpollack I don't live in the US, but I'll look for alternatives similar to foxfarm light warrior soil/roots I can find here..

You'd use an alternative to those two as a first soil, meaning they grow for a while, but you'd have to transplant into something hotter. After looking online I did see a soil called Canna Terra. I don't know if it equals ocean forest, but really look for a soil that has similar ingredients and quantities if you can determine that much. Weaker soil for little plants, stronger soil for bigger ones.