Axolotl has weird lips

[DiBs97]

Hi everyone! I have two axolotls both around 4 years old and so far they have been healthy. In the past couple of days I noticed that the lower lip of one of them has become kinda white and seems inflamed. His behavior is still normal so he doesn't seem stressed and eats normally. The other axolotl is completely fine. I took a couple of pictures that aren't great. Have any of you had this happen before or do you know if it's some sort of fungus?
Thanks a lot for any comments or advice

 

[wolfen]

there have been cases of axolotl having cotton mouth symptoms, if it gets worse then methyline blue baths might be an idea, see here for details Tubbing and Safe Meds - Oregon Axolotls