There are two ways of feeding in the fall. Traditionally it has been a 2:1 sugar syrup method. The idea is twofold. 1) The bees will feast on sugar syrup instead of their winter stores and 2) they will convert the sugar water and stuff it in the frames for winter use.
The second way is to feed the 1:1 mix. The 1:1 mix is fed for a different reason. And that is to make them think there is a nectar flow. But we want to add protein to the mix. Burn’s recipe is to use 1:1 and per quart, add 1 teaspoon each of Honey Bee Healthy Feeding Stimulate and Honey Bee Healthy Amino B Booster plus a pollen supplement. I use Pollen Pro. You can get it at Spence. I have had an amazing amount of bees produced this way and I have talked to others that have begun using this and it works well. If you weren’t adding the protein then that’s most likely why your bees are light.
Winter bees are starting to get laid as early as late august but mostly September and October. Ideally you want a minimum of 6 frames of bees/brood going into winter. Six frames should give you about 40,000 bees.
As far as the mites go, I would vaporize them with Oxalic Acid. And that should work well if you have little brood. I wouldn’t use Apiguard (thymol) because the queen will most likely stop laying. Time is running thin to produce bees, but you should be able to feed that mix, treat and produce bees in October. Remember that once the temperatures drop to about 50 degrees the bees can’t convert the sugar syrup and at that point, you’ll want to remove the feeders. And begin to arrange the frames for winter success.