The weather looks like it is turning colder, maybe for the duration. Feeding colonies will becoming much harder to do. The bees maybe reluctant to take down syrup when it gets cold. The bees do not like to ingest cold syrup. It may work to put warm syrup on the hive during the warmest part of the day. The bees may take it down, but as the syrup cools, the bees may stop taking the syrup down.
October is the time of year to treat hives with Oxalic Acid for a last varroa mite treatment. Oxalic acid is used this time of year when there is no brood in the colony. The lack of brood in a colony, give the varroa mite no place to hide and any Varroa in the hive are located on the bodies of the bees. With no capped brood to hide in, the Varroa mites are easily killed by the Oxalic acid treatment. Beekeepers who have fed late into fall, may still have a couple frames of brood in their colonies, making Oxalic treatments less effective.
Oxalic acid should be done when the outside temperature is 40 degrees at the time of treatment. It can warm up later in the day, but at the time of treatment it should be forty degrees. Here is a couple videos on how I treat my bees with the dribble method and using a vaporizer.
Dribble MethodVaporizer method