Do those cups have drain holes cut in the bottom? I had curled down leaves so I cut back watering and they got nice, long and straight.

Does that soil have nutes in it? Guano? Burnt tips could be nute burn, but those baby leaves (round ones) will normally wilt away. Have you yet checked the PH or flushed, sooner or later you will. I'm just throwing ideas out there, lots of variables could effect things.

Keep those small lights close, but not too hot either. Sounds like a fun little set up. Enjoy!