To me, some of the scales look dry. Sometimes when snakes shed and the humidity wasn't high enough the molting skin will take some parts of the skin with it, making some of the scales feel more rough or sticky-ish. This has happened to me a few times, so that's why I think it could've been that.

From what I have seen, scale rot normally starts out on the underside. But, the scales that look funny could also be bites from a rodent as dr del said.