Check out the stickies on shedding. Part of the shedding process is for them to have pink bellies. I don't know if it's the same as what you are describing but it would be worth a peek. Somebody will without a doubt correct me if I'm wrong. I think the shedding sticky is over in the General section.

I understand that scale rot will come from the substrate being too wet. Occasional misting won't or shouldn't do it. So, unless your tank is wet, it's probably something else. But, don't take my word.