tl;dr: Frame of emerging brood looked lethargic. Why? What to do?
I captured a swarm and installed them in a 10-frame deep with a half gallon of syrup in a top feeder, plus a couple honey frames from another colony. Two weeks later they had eggs and larvae and most of the frames had been drawn so I gave them another 10-frame brood box with new frames. Two weeks later they had brood of all ages and a good-looking queen, which I marked, but one frame looked a bit odd. Most of the brood area had emerging bees. Many of them weren't completely dead because their antennas were moving, but in the past when I've seen emerging brood it would be one or two per frame, and they'd be out in several seconds. In this case, the brood were just kind of there, not in any hurry.
Has anyone seen this? What does it mean? My leading theories are: moderately chilled brood (due to small nurse bee population), poor nutrition (upstate NY has a semi-dearth in summer and I didn't feed pollen patties), or some brood disease (possibly spread by varoa mites) combined with hygienic behavior. On that last point, I didn't notice any larvae with obvious foul brood symptoms, and I installed Apivar strips as soon as I transferred them from the swarm trap to the 10-frame box.
Later I saw them haul out an almost normal sized worker bee that was alive but a bit white-ish and could not fly, presumably one of those "emerging" brood.
Other than that the colony seems healthy -- honey and pollen and brood of all ages, no deformed wings, etc, etc. Their population is a bit small, but that's to be expected from a mid-summer swarm.
Thanks for any advice!