There is always the option of allowing the dogs to fight if they are already co-habitating together. This is how Alpha is established and maintained. Scooby and Shaggy have done it a couple times a week. It last for about a minute and then they are the best of friends.
Right now it is happening a little more because Shaggy has a secret desire to be the "Alpha". Scooby is a little weakened by his stroke which henders him from being the strong Alpha he was.
My advice is watch HOW they are fighting. If they are going for the 'jugular" (Thoat) then don't get involved! This is "Kill" mode for a dog. They kill by ripping the throat out. (Sorry gross). That is how they would kill a a human as well. So STAY away from dogs who are this aggressive as they are acting on complete animal instinct and hurt you.
Emergency situation: Throw an object to distract them or throw water on them either hose or bucket. Don't RUN TOWARD the dogs!!! They will turn on you! NEVER MAKE EYE CONTACT WITH A DOG AND WALK TOWARDS IT!!! This is taken as aggression. Simply look above their head and backaway.
If the dogs are "Playful or Establishing dominance"Fight this can be handled differently. Usually this type of fighting involves gnarling teeth, teeth to teeth biting, and some wrestling. This perfectly normal and dog behavior. DON'T GET IN BETWEEN THEM IF BITING! Simply call the dog's name if they are being too aggressive to each other. Get a treat or a toy to distract them. Soon they will start playing nice again.
If they fight too often, and not over food/toys, then you may need to separate them. One has to be Alpha so let one always be "Dominant" over the other and let that one ALWAYS win the fight. I always treat Scooby as the "Favorite" and the other dogs know and respect that. It keeps the pecking order in line.
Sounds like everything is okay in your house. Just a little dominance behavior. My dogs have survived 5 years together!