250 watt hps seedling issue

hey,i am doing a grow start to finish with a 250 hps that has a duel spectrum bulb.I am just wondering how far off the seedlings to keep it.At the moment it is 20 inches away because the seedlings are only 1 week old.BUT they are not fairing very well ,i wonder if i move them closer will it help them or will it be too strong ? or is it ok to just use the "if i feel the heat with my hand it is too close if i can't it is ok " line of thinking.

yea dude just feel the area near the seedling with your hand and see if its too hot. 20 inches is good for a seedling. you could even movie it up a little depending on the size of you grow room. maybe there is another factor to why its not doing well? do you have a picture?