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Remove the feed if it is still in there. I would close off the screened bottom. That open screen likely makes it easier for the smell to escape and be an attractant to robbing.
Is that your only hive? If you have more than one hive, the robbers may have come from your other hives. Reducing the entrances of the other hives helps make it more difficult for the robbers to perform their mission.
Leaving a screened bottom 'open' is controversial, in my opinion. Too much airflow is not desirable. Note that bees cool their hives via hauling in water and evaporating it - similar to a swamp cooler in a structure. If the outside air temperature exceeds 94 F, then having lots of [hot] air flowing through the hive works in opposition to the bees efforts at evaporative cooling.
I built screens into my bottom boards, but do not leave them "open". They have oil trays beneath the screens, and the design effectively blocks bees from the tray and airflow from moving through the screen. An alternative to oil in those trays is lime or diatomaceous earth. If you want more ventilation add a top vent instead of an open screen bottom.
. . . . . . "Reality trumps ideology." - - [Crofter - 2017]