There is also a bacterial infection that when becomes toxic and enters the blood stream..first looks like a slightly pink belly (streaked) almost like the beginnings of a shed.
When the scales turn brown, death follows soon after.
Anytime the belly is pink and shed is not expected....I would get to a VET just to be safe.
It's called Subcutaneous hemmorrhages and can be a sign of generalized infection or toxemia in snakes.