It's MY Rawhide
It is very strange to me that all of a sudden this happened. But, dogs do werid things. I think taking the rawhide away might be a good idea, for health reasons too. I thought that dogs really should not have rawhide because of blockage problems. But, that is a whole other topic.
I have a doxie too, she occasionally shows aggression when other dogs try to get her "Big Eyes" It is just a sqeeky toy that has big eyes, so we call it that. But, it is her favorite. When another dog comes near her she growls because she does not want it.
Even though you have had Sophie since the summer, maybe they are still trying to figure out who is boss in the heirarchy of the dogs. Did you ever give Sophie and Rocky a rawhide at the same time? Or, did you ever give Sophie a rawhide and not Rocky? I would wonder what the reaction would be of Rocky?
I would also talk to your vet. Maybe they might have a suggestion or maybe they have seen this happen before.
Hope everything works out.
"She is your friend, your partner, your defender, and your dog. You are her life, her love, and her leader. She will be faithful and true, to the last beat of her little heart. You owe it to her to be worthy of such devotion." - Unknown.
"Dogs are not our whole life, but they make our lives whole." - Rogers Caras.
"Somedays you're the dog and some days you're the hydrant."- Unknown.