can someone help diagnose

I was wondering if anyone can tell me what's wrong with these. They're 4 weeks old, the bushier one is electric fruit punch x white widow and the smaller is gelato. They were doing fine then kinda slowed on growth and the leaves seem to be slimming and clawing/ curling. I'm reusing ffof soil I read mixed reviews about doing that so I started with these 2 plants before I tried it with more. I'm using tap water and just recently started aerating it. At the moment I'm using fox farm nutes, well I was barely gonna give them the first feeding, I'm waiting on compost for future grows.

standard nute burn ...adding more perlite is the best way to stop it or even a serious flush,
3 times the volume of the pot, but it was your choice to re use this soil ...live and learn?

Yeah, thanks. That's why I put 2 in there before I used the seeds i purchased, so that I could test it and learn.