good luck with ur grow....personally id say give the pot a water till run off. This happened to me once so i dug around the middle lifted a patch of soil which contained the seedling...gave it a thorough water and put it back. watered after 5 days. Get used to the weight of a JUST watered pot and a dry pot. A wise man told me to grab two pots...one with just the medium filled and the other with ur baby, compare the weights and u will no when to water.
Improving ur RH just add a bowl of water and open ur cab doors during light out for natural air exchange.
Lastly turn hps off..get the plants as close as u can to the LEDs. HPS wont be needed for at least another 3.5 weeks. Make sure u LST her from day 8/9, bend her straight 90 degrees when she is at least 3 inches tall.
Good luck shadeyman