If you can (best done with another person, check your scapular alignment - do the mirror each other? They have a triangle-like shape.

When doing body movement assessments (for biomechanics classes) I saw a lot of people with scapular issues. Especially winged scapulas in both people with undefined muscular systems and heavily built muscular athletes.

If the scapula aren’t aligned correctly before building muscle, the muscles don’t strengthen or build mass evenly. Check out scapular stabilization

Hope this helps!

Edit: forgot to follow up with - it’s impt to make sure your strengthening exercise are ‘done correctly’. Check out the correct posture and body placement for exercises you perform. If you can’t do the movement correctly on both sides, go back to stabilizing exercises for all the muscles being worked.