2000w??? Wow, seems like overkill to me at this stage, seedlings and young plants don't need that kinda light just yet and yeah, heat stress could be an issue. Just make sure there's plenty of distance between them and the light, when you put your hand at plant height, you don't want to feel too much heat. How are your temps, anything above 85f. is going to start to affect growth? 40% humidity is fine, it can get up into the 50's no problem, although lately I've been having problems with a leaf fungus when I let it get that high so I keep mine between 35-40%rH.
Also don't foliar feed under intense light, and I personally don't anymore, just seems to cause more problems and watering the roots seems to be enough, imo. Finally, aside from it being part of the natural cycle, it seems to me that my girls just look better when I give them a nap during veg, so except during the seedling stage which I do run 24/7, I don't go over 18 hrs of light (plus saves 25% on your light bill ;?).