hard to say bakers, i went back and re-read what you said. if i lose a strong hive in the fall or before december, first i always suspect that it is typical of a mite problem but you said you had treated.
"there were dead bees on top of the inner cover, on frames, on top of frames and a huge pile on the bottom board in the center.
1. Found thousands and thousands of dead bees on the bottom board and a few dead still on frames and on top of inner cover. No bees had their heads in the cells.
3. Found sealed brood in the bottom and top box.
4. Found stores on the outside frames. The bottom box is really heavy with capped honey.
5. I had put fondant on top and it was consumed. "
just a wild guess here, with dead bees on top of the inner cover, with no fondant left, stores to the outside, and bees piled up in the center......
i would think they may have 'chimneyed up'........? and maybe died from cold starvation?....they covered the brood, and didn't move to stores on the outside. i would think though you would find dead bees in cells? they will crawl in cells to help 'heat' the brood.