Hi,
The drop in the shoulder in your case is due to a mild spinal rotation. You have not send a back view but i suspect it is mid thoracic.
If you are doing any diagonal exercises like wood chops etc, make sure that you do left rotations.
Now this is not a structural issue but is function so some releases and rotatory exercises should help. You would need a physiotherapist appointment for this!!
From your photo i coudnt help noticing collapsing arches (Rt more than Lt). Might be good to do some single leg bridging both sides for increasing your glut muscle strength.
Next Steps
Under specific guidance from a physiotherapist please look at starting diagonal exercises after releases along the back.
look at core and gluteal strengthening