my red-sided male has a couple

[Cazador]

Reed, best to leave peroxide alone, it could do more harm than good. Iodine (betadine, pevadine) will do the trick. Also it is very important to keep the snakes' enclosure very clean.

... and DRY. Sounds like scale rot, which is a fungal infection that has more growth "within" the snake than it does outside the snake. It's like the small portion of an iceberg that is visible. Betadine and providone iodine work well as do some of the anti-fungal creams (Tinactin, Micatin, or Veltrim).