My aggression issues were not caused by my 1 1/2 y/o pitty it was by my 8 y/o mastiff. I felt it was a dominance issue showing my pitty who was the leader. One day I couldn’t separate them fast enough and my mastiff ended up with 12 staples and my pitty received minor head wounds. What I found in my home that has worked great is the crate and rotate method. Everyone gets time and everyone is safe.
Check out http://www.PBRC.com they have amazing information on numerous subjects petaining to pitties.