I recently upgraded to 400w hps for my 2.5x2.5x6 grow tent. I got a perfect ventilation system but when i am using the 400w, the bulb has to be 35 cm away from my plants, in contrast with the 250w that has to be 15 cm away, in order to have 80f temperature. I got 4 plants, which do you think is the best bulb to use?