This seems to be partly genetics, early training in life, and the “priority principle”. I think I read somewhere that early on Arnold had the same issues and my prioritizing his workouts and learning what shapes what, he was clearly able to even things out into a state of perfection. Basically work your weak parts first when you are working out.
I notice I have a side that is stronger than other with certain muscle groups. Doing Berardi’s workout (#286), I’m primarily doing barbell excersies, so what I’m trying to do is concentrate on squeezing/contracting the weaker muscle a bit harder than the stronger side…its seems to be helping me reach a balance.