how close to keep lights to youngens

I have four clones and six seedlings that are at about the one week mark. I usually don't count the first seven days as a plant is hardly photosynthesizing in the germination stage, i.e. it has been two weeks and a day since they went wet. The clones have comparable root systems so I figure they are about the same age - one week.

The seedlings are all Afghan #1 and I had to use Superthrive to get some of them to make a comeback; many of the seeds I got were immature and one was damaged (crushed). That is too bad. I have heard such good things about Sensi Seeds too. No worries, though, as I have six strong plants. I hope the hormones don't give me herms or too many males. I will be laying off them for a while.

The clones are three White Widow ladies and one Sour Diesel. One of the WW looks pretty weak.

Currently, all of them are sitting with their tops about a foot from the glass barrier in the Radiant air cooled unit I have. One Grow Lab (don't recommend them - weak fabric around the ducts) has 600W of MH going and this is the one with the Afghani #1's. The other has 600W of HPS going over the WW and the SD.

Should I be alright?

for a 600w HPS you can get it as low as 12-15 inches & maybe even closer if your lights have cool air running threw them.

Just put your hand under the light to check how hot it gets.

add really weak cross-wind fan on canopy and u can put em real close (nu clones can wilt easily from fan). always start far away from light w/ young and gradually intro over a day or three. u probably already guessed this much. peace... good luck. do u know any of yer sour diesel origins... how is it?