Im growing 11 plants in a 25 sq ft room. I have a 600w HPS. my last grow of ten plants was a bit of a dissapointment. I yielded aproximately an ounce per plant. I attributed this to the small pots (3.8 qts) I used and have since switched to 7 gallon containers. Should I add another 400W or 600w lamp. What is optimal?