heres the deal about seedlings and humidity, i use rockwool 1in cubes, this goes for clones too, they love humidity, the dome serves 2 purposes, for one they love it, 2 higher humidty under lights will keep your medium from drying out, whether jiffy plugs or RW, this is key, cus you do not want to keep soaking your plugs, just moisture, pick up your plugs or cubes and see how light they got, i use a spray bottle and give the cubes like 3-4 pumps everyday or other day. i got seedlings going now and i wanted to get the floros closer so i had to take the dome off, with this in mind i pay close attention to the moisture level, since your already not having problems germing and raising seedlings, you should just about now be getting a good feel for how moist to keep your medium, do not spray the seedlings themselves, also did you watch seemorebuds yet? also clones and seedlings like humidity from 60-90%, once your seedling is established and/or your clones are rooted, a safe zone of 40-60% humidity is just fine, even at 70% i have never had problems