I had this happen to one egg last year and some told me about the anti fungal powder but I was worry to do it.
So what I did was every day or so I would just open the lid to the eggs and the one with the mold I would take a dry Q-tip and roll it just the spot clean, make sure you don't spred it around and the egg hatched out fine.
I'm sure there are others on here that might help you out better then this but this is a little something to try.