I would make sure they have lived outside for a few months to acclimate. Fatten them up as much as they will eat before they stop for the winter. They need to be off food for a couple weeks before the hibernate.
So I've been feeding them a lot but the male box turtle still feels light. Should I leave him outside? Or keep him outside and keep feeding him? It's gonna be in the 30s tomorrow for a few hours.That is good, find a place where you canloosen the dirt down a couple of feet. That will be where they likely will hibernate.