I had a colony be usurped by another early this year, and I've been loving the new bees so far, so I split the colony on 4/21. I moved Queen Ravenna, a frame or two of pollen, and all the capped worker brood to a new hive, and I left the original hive with all the open worker brood and several frames of pollen, and I gave both colonies the last of my stored partial honey frames from last fall since our spring flow didn't materialize. On 4/29 I checked the original hive and reduced their queen cells from 12 to 2. I didn't notice anything unusual during this inspection, although I was predominantly focused on find queen cells. Before I did the split I checked their mites via sugar roll and it was 0. I've done a sugar roll on them every month since the beginning of the season and haven't found a mite yet. For reference my other colonies are around 0-1% right now.
Yesterday or maybe the day before, I noticed a small crowd of foragers on the landing board of the original hive. They were kind of just standing around, a few were sharing food via trophallaxis with each other, I noticed it but didn't really think anything of it. Today at about 3:30 I went out to look at the bees and both halves of this split have a decent pile of dead bees out front, maybe 100-200 bees, many of them drones, just right off the landing board in front of the entrance. Also the crowd of bees on the landing board of the original hive was conspicuously larger today, maybe 20-30 bees. Still some engaged in trophallaxis with each other, but some of them were walking around almost on tiptoe, vigorously trying to clean themselves although none appeared to have anything on them. Many of them looked overgroomed, with hair on their thoraxes and/or abdomen missing, and few were almost entirely bald. Most of them were older-looking foragers, and several had pretty tattered wings. The new hive with the queen had normal looking traffic, although a bit lighter than the other hives since their forager force is still pretty small, but that would be expected. All the other hives in the yard look normal.
Any thoughts?