His mouth seems really pale to me as well but that could just be the camera ( mine changes the colours of everything and I can't work out how to fix it yet),
But yeah It does look abnormal - hopefully its something easily treatable **crosses fingers** and hes back to 100% soon. The fact it's in a few places though is kind of worrying and might mean its quite well spread or in the bone ( that's worst case scenario I think so don't panic just yet).
I always thought mouthrot presented more as cheesy yellow deposits covering most of the redness - but it's been years since I saw it.
dr del