pitbull fights

Hey all

Just a question, iv had pitbulls befor and had no problem. I now have two pits again, a female and a male. The female is a 11 months now and my male is 6 months. They have been fine together but recently the female seems to be getting agresive with the male! I havnt seen why this is but only hear them fight and hear the male cry. Everytime this happens its over before I get to them or as soon as I see them they stop. Is there anythging I should be worried about for the future? Can anyone help with some advise?

Thank you