Hives 2 and 5 have died out. I can't see any obvious reason; neither had touched the candy I gave them, though both were very short of stores. They don't show the normal signs of starvation, so it's not isolation, when a cluster can't move over to food in cold weather. The overwhelming majority of my losses involve first-year queens, so it has to be something to do with the queens. They weren't mated in bad weather, or when there was a shortage of drones, so it's a mystery. Losing half my hives is a major setback!