Bees will clean up mold in a big hurry with no bad consequences.
 
I'd be more concerned about what caused the death.  You wrote that honey was
present.  If bees die of Tracheal mite infestation usually in January, but
maybe February, there will be few dead bees on the bottom board, and just a
small group clustered for warmth, but lots of perfectly good honey, even 50-70
pounds.
 
Further, it does not sound like you had an upper entrance to let winter
moisture out of the hive.  The best upper entrance is to cut a 1" slot in the
front edge of the inner cover, so that bees (and moist air) can crawl through
that cut out slot onto the front face of the upper hive body just inside the
edge of the telescoping cover, walk down the face of the hive maybe 1" and fly
off.
 
Cold weather does NOT kill bees, or bees would not be kept in plain hives in
Alaska, Canada, or Maine.  Something else other than COLD killed your bees.
                                                          George Imirie