I think you're good. That's just my guess without being able to see what you see. Bees die everyday, if they are locked up by cold weather they will accumulate on the bottom board until it's warm enough to fly then the girls will start dragging out their dead. I was SHOCKED the first winter by the piles of dead, figured the colony was a gonner, May rolled around and BOOM! they really took off. That's my thoughts, we'll see what others have to say. Ted