Alas, I had to remove my cories from my sorority for that exact reason: they pigged out on the cory food and the cories got none. I would drop the food all over the tank, even hide it in the PVC pipe hidey hole, and the girls would divide up and roam the tank looking for the food spots. They'd literally shove the cories out of the way. Even now, I have one female in my community tank with cories and she tends to pig out on left overs and swell up like a blimp.
If you find a way to feed your cories without the girls eating too, oh please let me know your secret.