Behavior issues

Just looking for some quick advice. My male rescue (age unknown fixed) and female juvenile used to get along well. They stay in a 2 story hutch while I'm gone but generally free roam when Im home. I've noticed hes started being more aggressive with her, chasing after her and keeping her away from treats and water. I can separate them while in the hutch but not easily when out. Is there a way to fix this behavior? They have been housed together for over 8 months without issue before.