So we've starting feeding both hives with syrup, in order to get them all ready to start harvesting honey. However, in feeding of them, and in expanding their openings a bit more, we've noticed some problems with the hive that was more productive last year. There's this black tar-like substance (Update: probably bee feces) on all of the wood and also in the combs, and the bees have done a very poor job of cleaning their hive: there were hundreds of dead bees left on the bottom that should have been removed from the hive. I'm hoping that both of these things were just because the bottom door was too small, or it was too cold for the bees to clean the hive, and now they should be able to clean themselves out. However, it could be a bacterial disease, which will likely kill the hive. We'll see what happens, and will be talking to our local apiarists.

Update: it appears it's nosema or some other type of dysentary. I'll still check with some kind of expert to confirm and for advice on what to do, but i don't think it's as bad as if we had foulbrood, as it's something of a common thing to happen when you don't have enough ventilation in a hive during the winter or it's too cold for the bees to defecate outside.