yea those plants are stretching a whole lot
get some mylar and put it all the way around the lights and plants as close as possible
a 400 watt MH/HPS i found works best with about 4 or 5 plants
so yea get some mylar and consider getting rid of some of the plants that arent doing to well (stretching alot, burning, or the clones that had the mites) your results will be way better if you didnt have so many plants to get the light out to