I don't have a great deal of Hight. my grow area is 1.2m wide x 3.4m long. I've got 2 cool tubes with a cool hood in the middle. My leaves started going light and yellow, you can actually see the plants darken as they are away from directly under the tubes. but I was dealing with a thrips problem, so wasn't 100% sure if it was being caused with all that, now with some investigation, It light burn. I got 3 600w hps. thinking of going to 400w. my question is. should I change them all too 400. or perhaps just the middle. will I lose a lot of weight changing to 400w.