Are you using HBH or Oils at all? Anytime that HBH or essential oils are used the bees will continue to take the syrup all season long as it lowers the PH of the syrup to that of honey. And as you know bees love honey. They will take it over the wild necter sources available even in a FLOW. So if you are using either one, stop the use and see if they will just take straight 1:1 syrup alone. If they do then there isn't a flow on but as long as they have stores, it's fine to quit feeding.