Looks like a type of fungus... However, the one has roots on it. I would just rinse off the mold with clean warm water and then put them back in the tank. The one may sprout if those are indeed roots (the longer white things).
I have about a 50/50 success rate with these bulbs. They are cheap and indeed worth it in my opinion even if you have a few failures. They grow very fast once they sprout.