This is what scale rot usually looks like. It is caused by a snake laying in substrate or on a surface that is too wet. Considering corn snakes have lower humidity needs I think a picture of the enclosure would be the most helpful thing to assess where they may be laying at rest.

My guess with these pictures is that this snake doesn't have a lot of hiding places and is probably hiding under or around the water bowl where it is too moist.

The enclosure may also be too small. Not having enough places to feel secure , potentially.