I'm no expert at all...but I was watching the Dog Whisperer the other day & he basically had the same situation. You need to assert yourself as the pack leader & let them know that this is not acceptable behavior. NO yelling, no words just a short sound and YOU confront Joey or Apolo (depending on who's starting the fights) & let them know this is not acceptable. He confronted the aggressor & made the dog sit & relax & he made the dog stay in his submissive relaxed position. Once the aggressor was relaxed he held on to him with a leash & brought the victim dog over & made sure they were both relaxed (Cesar between the two).
hope this helps
Basenji Mom of C3PO & TOPAZ