TReat for mites first and foremost! I personally favor apiguard for a stronger colony such as yours or Oxalic acid vaporization. I do sugar rolls to access my mite levels and directions for the procedure are on facebook or detailed here in old posts. OA vaporization would require a relatively large initial investment or a loan from another beekeeper. By your narrative the colony seems well provisioned. The way you are feeding, a constant flow of pretty dilute syrup will keep the bees raising brood past the time of year where they should be shutting down for winter. I personally weigh the hive and if it is 125-140 lbs, they no longer require feeding.