Hydroponic Seedling issues

Hey All,
New to the environment, but seems like an AWESOME place to be! Trying to get crop going, but seedings keep wilting in the cloner? they germinate, sprout and then some, not all, begin wilting and then keel over? Some remain healthy? I have moved sprouts closer to the 40W flour of the cloner, and have turned fan on for some fresh air. I water about every three days and the 1in rockwool seems just about right when i water a little moist, but not wet or dry. I mixed a little, couple of drops, of Hormex to my watering solution and it is 5.8 Ph. My question is, Is it normal to lose 40% of your seedlings? I plant about 10 each time and it seems out of 10 I wind up with 5-6 healthy looking plants. Also, as a neophyte to this process, when do I move them from the one inch to the 3 inch rockwool? The healthy ones have a few roots protruding, is it time? I am running a BC Northern Lights Producer for the plants with a 125W FS Flourescent for the Veg cycle. I don't want to move them too soon, but I don't want to lose them either? How long can they stay in the clone dome?:smokin: