hello, i have 2 large sprouts, about an inch and a half in length, 1 medium sprout, around half an inch, and 2 more that are barely out of the ground. the bigger ones look like they are already starting to stretch, and i have my 400 watt HPS system 3 feet and 3 inches from the soil. how close can i get to my sprouts? i dont want stretchy weeds. but i also dont want to burn those little puppies out either... thanks...