Welcome to RIU MLP,
everything appears to look ok from your pics. I imagine you'll be transplanting them to their final pot soon. I would put them down deeper in their next pot about a half inch from the coytle leaves. This wont have any adverse effects on them, although new roots will begin to sprout where you covered the stem with soil. Your flouro tubes will be fine about an inch from your little ones. Is that new rockwool you are using? It souldn't stay sopping wet at the surface, it should feel damp. You could actually bump the light to 24 hours, without adverse effects, actually it will help. After about 2 weeks or so you can cut it back to 18 hours just to give them a chance to rest. Remember during the night period the plant will grow roots. This also the time you should start feeding nutes. 1/4 strength at first and increasing every 5+ days. What nutes are you using? Follow the directions on the container but start a 1/4 strength. After panning back thru your thread, I didn't see you mention anything about pH. Get a meter or some way to check this. GH - General Hydroponics makes a pH test kit with the test reagent, a test bottle, and pH up and down. Test your tap water after sitting for 24 hours, Adjust it if necessary to about 5.8 to 6.0 Use this water to give your little ones a drink when the soil is dried out. Most new growers will over water the youngsters. A moisture meter will help with the watering, but your finger will work just as well. If you poke your finger into the soil up to the second knuckle, remove it and place it on your cheek, if it feels cool, dont water. Or if soil is stuck to the end of your finger, dont water. If it's moist enough to stick, its moist enough for the little ones. Well this ran on quite a bit, check out the grow FAQ button at the top of the thread, and read, read, read.
Otherwise, it's all lookin good. Hang in there and be patient.
Nim