Well..i have 0% experience with mouth rot but ive looked threw a few pages of images on google about mouth rot and it looks like it could be a early sign. Some of the pictures have small spots like that but there usually darker...so it might not be.hmm..
Sorry i wasn't much help...id keep a close eye on it though.
(btw- if you google image that, be warned, some of its pretty nasty)
Mike~