keep in mind plants grow beneath the surface of the grow medium as well as above it. when roots are growing the tops of the plant usually arent...i had my light as close as i could and they werent growing much even though the temp and everything was good. so i want the 400whps light as close as i can get it without burning ?
You want the plant's energy going to the buds & not to the stem by means of stretching..dont u want them farther back for the plant to search for the light.