My 1st plant needs Help!

Heys guys, this is my first growm and im trying hydroponics (DWC) in my pc tower i built. It stays on temp betwwn 79-82 with humidity 16-24. my frist true leave were starting to get discoloration but i dont know from what.....i have to 2 grow books and practically read them both..... my ppm is only 300 cause its a seedling still. Another question. this is a sativa from a seed bank (mixed bag). am i wasting my trime with a sativa in such a small space. maybe tie the girl down?

why the hell do you get the humidity so low?
you want it around 80% at this stage. You could use a humidity dome (bottle without the neck) over the plant to raise the humidity until it gets better.

I believe your wasting your time with a PC grow in general and that a straight sativa in a PC case will luckily yield you a couple of joints.
Its a fun experience and all that but really, don't expect much from a PC grow. not yield and not potency wise.