causes? Some of the bees might have jumped to the right hive
Queen is not a good queen
Left hive is buzzing away. All frames in bottom hive box active with both honey and brood. Except for one thing - brood is not well patterned. While I've read that new bees and workers may need time getting brood sorted out, my bee advisor, Al, did not think the hive was doing well. During my inspection, I did not see the queen, but I was not overly worried as I did see enough brood activity.
Al was going to throw a new nuc in the left hive and was going to take a look at the right one again. In the meantime, I'm still feeding.