I'm sorry about your dogs fighting!

A good way to break up a fight is to spray them with water, or dump a bucket of water on them (not a good idea if they're inside though!)

Daphne got into a fight once and we put a chair over them to try to break it up - but it wasn't a good idea and they became more agressive towards each other. :/ Luckily that was the only fight she was ever in though, and eventually we broke it up.

If it's happening more and more lately, I'd seperate them when you aren't there, and talk to the vet about it. Maybe you could find an animal behaviorist?