Have used Apiguard for the very first time & had a few issues, just want some opinions.

Firstly, it's fall here so it's the fall mite treatment. The hives have had honey removed and are in two deep boxes ready for winter. Mostly, the top box is at least 3/4 full with honey. The method I used was to lift the top box, and put the cardboard with I scoop of Apiguard gel on the top centre of the bottom box.

Most hives are still strong but a few are not, so for those ones I put an entrance guard on, with an entrance 4 inch wide by 3/8 high. No top entrances. Temperatures have been down to 60 ish night, and 75 ish day.

Problem being a number of hives have been robbed. I'm picking it's cos the bees have ben disrupted and driven away from proper entrance guard duty.

What have I done wrong and what should I have done?