Poor you, stoats are definitely one of the trickiest predators to stop. What a nightmare. We had a youngster that took out some of our growers post harvest. Just so damn quick.
Feed wise, I'd personally get them off the corn as they will not need a warmth boost now indoors. I'd be more tempted to introduce some greens in, very gradually - or else they get the runs! Corn as a treat, toward the end of the day.