Is this the same colony that was such a slow start at the beginning of the month?
Do you have some other bees, so that you could start raising a couple new queens? I would start that process asap if so, then if you decide you don't need to requeen, you can cancel the process or share/use the queens.
They also might have brought some disease from wherever they lived before, a late "swarm" might have been an abscond. I've caught such a swarm, and they were deadout two weeks after I hived them. Sick bees. so I'd be also unidirectional about moving resources to this hive but not from it, until it gets sorted.
Get into the brood nest and take some good pics, and post them here. We all like to look at bees, and there's some experienced eyes around "here".
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