uhm I cant really tell by pictures, but I can say if it looks like white fuzzy stuff it may be from a cut from a bite or he may have scratched his head on something, if that is the case and it looks like white fuzz then you should be able to treat it with salt and higher water temp. I saved my JD with white fuzz that way. My bf and I have a pair of Jags and they got clear mouth/white fuzz and we treat them with Erythromycin we bought at petsmart and it worked as long as you keep up with treatment/water changes. Erythromycin is also good for HITH its $15-$20 you can also get it at a Vet's office usually.