Hi, I started seeds for the first time last year. I used the trays with clear lids and a heat source to warm the soil to around 85 deg. f. Within a few days I had mold on the soil! Too much moisture with no airflow under the lids. I think I just removed the lids and let the soil dry out which killed the mold. The plants were fine. For the next round of seeds I made several holes in the sides of the clear lids so that air could pass through. That seems to have solved the problem. As soon as the seedling emerge I remove the lids and get them under the lights. I think you just need to remove the lids or add some holes for ventilation. Hope that helps. John.

So maybe I was panicking over nothing; I was afraid they were ruined. I will definitely remove the lids now, and give them some air, and poke the holes, too. Why do the directions say cover with lid till they emerge if that causes mold? It seems more logical that they need the air circulation.
Thanks John!

If you know that you can keep the soil from drying out without using the domes, I think you're actually better off not using them. This would be possible for folks who are home all the time and who are not trying to germinate a lot of seeds at once. On the other hand, lots of trays would be hard to watch that close and impossible for working folks who are gone all day.