One of my hives swarmed this past spring. The old hive made a new queen and she was laying but her patterns seemed a bit spotty. I thought that was probably due to the spring flow having ended. Well they steadily went down hill - neither mites nor shb seemed to be a problem - there was adequate honey left for them to make it. But after checking the hive last week the last bee was gone. I had even moved them into a nuke box so they wouldnt have so much space to take care of. What are the most probable causes of this? I really dont ever remember a hive that swarmed dieing out the same year. A weak queen?