Two puppies aggressive when playing
We have two puppies one pit and collie mix 9 months old and one cane corso and pit mix 4 months old both are male when playing the are fine for a while then it turns to barking and showing teeth. The 4 month seems to start it he try's biting the toy ends up nipping the 9 month. I am afraid it will turn to fight. So now they play seperate and one on the leash when in the backyard. What can I do to help them get along while playing?