I don't know if yours fits this pattern, but this is what I am seeing in my dead outs and in other folks dead outs I have looked at. Last season, many of us got sugar roll counts for varroa that were very low--below threshold for treatments. Hives that appeared to be strong or at least reasonably strong going into winter dwindled to the point that fairly recently, as queens started laying, there were not enough bees to cover the brood and reach food nearby. I paid attention to the small clusters and saw that honey cells in the next frames within 2-3 inches of the cluster were empty while there was honey toward the ends of the frames. The bees would not leave the brood to go that 2-3 inches and starved in place.
My dead outs were on solid bottom boards and I could not get a good mite count. The insert of a hive I looked at 2 days ago had at least 100 mites in a 2-3 frame area based on debris drop. This had been a strong hive going into winter with below threshold mite counts. This mite count matches what some beekeepers with live bees doing winter OAV have been getting on their inserts. I don't know if this count is unusual, but it scares me--especially with so many mites available to attack new brood. I don't know if the mite numbers clustering with bees come from untreated "mite bomb" hives or are normal numbers. I am also wondering if mites are now carrying some more virulent viruses than before. A little over a year ago, one of our NC inspectors said he was seeing less DWV and wondered if what varroa were carrying had changed some.
I have gone into hives in the last couple of warm days here and made sure that I placed capped honey right beside the cluster. For my hives that make it, I am planning on much more aggressive mite monitoring. If folks have been doing winter OAV treatments with screened bottom boards and inserts, I would like to hear more about mite drops they are seeing so we can try and get some idea of what may be a "normal" winter mite count.
I hope I have not hijacked this post and gotten too far from what Mikey N.C. looking for.