They might be too wet. Like SeaMonkey said the rockwool shouldn’t be overly soaked. If you see fog on the inside of the dome the humidity is high enough. I spray the dome itself the first couple days, then nothing as it’s always foggy. If there’s large droplets on the dome I’ll remove it and wipe them off with a paper towel.
If you have water in the bottom of your tray dump it out.