I am fairly new at beekeeping and this is my first winter with hives of my own. I have 3 colonies. 2 seem to be wintering quite well but the 3rd has some unusual activity which I have no experience with. First of all I live in northeast Canada and right now we have close to 2 feet of snow on the ground. My hives are 2 boxes high and all three hives were treated for mites, Foul Brood and Nosema in the Fall. Now back to that third hive. In the last 3 weeks I have noticed that each time I pass there seems to be good quantity of dead bees on top of the snow and there seems to be a brown stain circling each dead bee, also the top exit hole seems to be stained somewhat and also along the front of the hive. the other 2 hives have a few dead bees which I beleive to be normal.Is this Nosema and what can I do about it?