I'm going to sound stupid saying this, but, are you placing your seedlings very close to your fan or ventilation system, perhaps they are actually just drying out.
There have been issues with grow tents that give of harmful gases when heated (with the light). Try removing them from the tent for a bit, see if it makes a difference.
The quality of weed around where I am was gradually getting worse, then i was unfortunate enough to smoke some "contaminated grade" and thought this has gone too fucking far, and started to grow my self.
youtube response ftw.
I would try and stay clear of airsoft, its all a bit "real". Go for paintball, way more fun.
Now realising hes 12, in all honesty id just say no. It always unnerves me seeing young kids running around with guns.