moat likely the problem, but could be Varroa Mites, they are feeding on the drone brood, You have them in both hives, as the brood was capped in the parent hive, They hatched with deformed Wing similar to k wing. You need to assess the mite load, and treat for mites, since most treatment will take care of both. you have expressed that you would treat with Mite-a-thol it is safe to assume you are not treatment free. so I would recommend hop-gard it your state allows it. if not Oxalic Acid vapor.