Scale rot?

I've seen a million posts on this, and I just want people's opinions. Does it look like it? It's only on one spot I checked his whole underside. I clean out his tank all the time I don't understand how it's possible if it is. Opinions?
http://i52.tinypic.com/15n3lav.jpg

What are you keeping the humidity at? I don't think it's anything.

It doesnt really look like anything much, id keep a eye on him and see how he looks after his next shed. My oldest boy got belly burn a few months back was a few inches long, i treated it and after his first shed couldnt even tell.

Humidity is about 55-70. I just don't really know what the start of it looks like. I got confused when I saw it because I'm so anal about keeping his area clean. But if you say it's nothing than I'll just keep an eye on it. Thanks for the quick replies!