Sounds like your using more of a compost mixture than an actual potting soil. I've been using shultz with no added ferterlizer and have had good luck. Any bark, leaves, ect. do bring up acidity level, that's why you have to put lime on your lawn if you have a lot of trees in your yard.
As for your lites, if you think you got heat problems from a 120w incondesant than watch out with the 400w hps. It will got HOT!!!!!!!!!!!!!! Yellow leaves from over watering or to much fertz. to early maybe I don't know. When you get the 400w you will see those babies grow, just watch your temp.
Later dude, Redeyed