Bulldogs World

Well I have a problem with both of my bully's..suddenly the past few days my girl Hannah is becoming increasingly aggressive with our male dexter..yesterday she aattacked him and then he engages in the fight and they bite each other on their fACes or mouths I'm horrified. I'm not strong enough to tear them apart I am at a loss ..they are both same age.  Hannah would prefer he not be around and dexter really doesn't care about anything but I see he now goes out of his way to avoid her... I'm scared don't know what to do and have had bully's for many years never had this problem..any advice would be greatly appreciated..thx candy