Man o Man am I happy to find this post. New grower here and my room has 10 Gavita Pro 1000s and my plants have looked more yellow and not as healthy as my buddies who has the same clones I do but uses more traditional lights in Adjusta wings. He has to have his lights right at the top of the canopy but I too need to keep these light 3 feet or more above the top of the canopy. Also, I as well have started to add CalMag and my plants started to look better as well. I am in a 50-50 mix of Pearlite and Pro Mix and using GH nutes. A week away from my first harvest and I tell you this has been a very stressful experience. Nice to read about other peoples experience using the same lights. I believe they are very powerful but it is a shame there isnt more support from Gavita on the little things like this that are important to know. I am also vegging my next batch right now in a new 8x8 room I made with one 1000W MH light and I have to say that the clones seem to be doing better under that light for vegging than under the gavitas last time. I definately will raise the Gavitas up more when these girls get into the main room and continue to add CalMag and play with upping the nutes. Thank you so much for this post! I thought I was going crazy