I would be a bit concerned about your reliance on OA exclusively. The more you use it subsequent times, the more resistant mites will get. Are you monitoring/checking their mite loads? If so, what do they look like?
Your queens may be getting suped due to overexposure to treatments. She is the only bee in the hive that is around for every single one. Folks who generally treat a lot, like commercial growers, usually have to requeen every year in late summer to make up for that.
Also, your queens will most likely not mate with drones produced in your apiary. Queens tend to travel much further away than drones are willing to go. This is a mechanism they developed that prevents her from mating with her brothers.
Your queens may be getting suped due to overexposure to treatments. She is the only bee in the hive that is around for every single one. Folks who generally treat a lot, like commercial growers, usually have to requeen every year in late summer to make up for that.
Also, your queens will most likely not mate with drones produced in your apiary. Queens tend to travel much further away than drones are willing to go. This is a mechanism they developed that prevents her from mating with her brothers.