I received a new hive from friend that needed some TLC. Barely made it through winter and needing to be fed. I put on a top feeder and things seemed O.K. Today I checked on them to add move sugar water and noticed mold growing on the inner cover. We have had a bunch of rain the last few days plus the temperature has dropped into the low 40's. I do not have the telescoping cover propped up slightly for ventilation like I do on my other hive in an effort to help the bees keep everything as warm as possible. Is this a mistake? Should I be worried about the mold? Any suggestions?