There have been several threads on here about imbalances, and I agree that prevention would probably be the best cure. Your program looks OK to a point, for the mid to upper back, and if you read through the threads, try them on an iso-laterak machine, or use DB's, starting with the weak side first. However, with what you stated, i.e. the problem being with the erector spinae (the large cord going up the spine), I would suggest adding in one or two movements that accentuate it. 1 arm cleans, or snatches, or swings, starting with the weak arm first.These target the back/core.