I lost 2 of my 5 colonies. Sad I know, but this is an opportunity to learn as well. The Flow Hive is doing great BTW, it was other colonies that failed.
I followed what I thought were all the right steps going into winter - I made sure the girls had food, I treated for mites in the late summer and early fall with oxalic acid vaporization, Apivar strips and I even used powdered sugar to get some mite counts before treatment.
I will say this - I had hive top feeders in place less than a week before a short cold snap hit and maybe that food changed the moisture levels in the hive as it never got capped. You can see a lot of uncapped, wet stores in the frames.Maybe that put humidity levels over a tolerable level?
I’d love any learned opinions.