I have some seedlings just up, and have them under a 400w MH 36" above them. I'm concerned about stretching, a problem I have had with unsuccessful grows in the past. Is 36" too high, too low, or just right? I know I will need to lower the light once they are vegging sufficiently. I have read various posts in searches and the distances discussed range from 2 feet to 4 feet, so I am not sure what to do.