Suspected reason for deferral, how to fix it?

Sorry, if I was a bit harsh. I just think you should be focusing 100% of your energies into making your other apps as perfect as they can be at this point. By all means, come late January/ early February, work on sending an update letter to Harvard. If you can point to some new and unique accomplishments, particularly in physics, it will help your case but it is still a long shot.