An observation.
Most times when I work with students that have dogs fighting in the home… the dogs have had no formal training. In other words, the owner has few tools to communicate with their dogs. Everything is being managed nonverbally and using the physical layout of the home.
With all dogs, it is a good idea to train them starting with each basic skill as they enter the home. The more dogs you have, it is more important that each new dog is also trained right from the start. Otherwise, they all are going to do whatever they want to do, and you have no influence. No manners. No control. The dogs have no idea what they should or shouldn’t do, so they do what gets them some kind of reward and they complete for those rewards instead of exercising any self-control and taking things in their own turn from the owner.
Plan accordingly.