I learned recently that if theres to much space in a hive( like too many boxes) the bees cant stay ahead of the moths...I lost 2 hives this year too...I just discovered one of the losses about 3 days ago.. It was a hive that I left a honey super on( I was gonna see if I could get just a couple more frames of honey before winter)..When I looked in not only was the one full frame empty of honey but the bees were gone also!And this was in a time period of about 3 weeks!
Thats all I know about that!

your friend,
john