They're different cups, different seedlings. I haven't fed them anything. Just whatever is in the dirt (Jungle Growth soil) and then i'm using tap water that I leave sitting out for a day.
I took a box cutter and cut lines down the side of each cup all the way around before I planted.. plus a few cuts on the bottom.. I'm thinking slits aren't good enough, and they need to be bigger holes... as if the dirt it clogging the slits I made or something. Idk
Oh, ok. Then the first seedling is doing great. The second one is having issues. Yeah, they need drain holes, not slits. Better drainage should help your situation.
Oh, look at me giving soil advice. Should I be doing this? Lol.
I don't know, it looks like it's starting to feed on the cotyledons to support its new growth. That's a sign that the roots aren't absorbing what the plant needs.
But if OP decides to go with "it looks fine," there's nothing I can do about that.