Help identifying a fungal infection

[Vashrine]

This is Bernie (see attached), he's about 4.5yrs old, just over 11.5 inches and I've had him his whole life.
I've literally never run into a single problem with him, he's truly a champ. About a year ago he developed a small white spot on the top of his head, his water quality was fine and I couldn't identify any other external stressors. It stayed unchanged until about 2 weeks ago and now I feel like it's a bit more present on the top of his head.. I'm just unsure if this is truly a fungus infection and am looking for some guidance. He's never been fridged so I'm a little apprehensive unless I know for sure it's fungus. I don't really see anything much in his gills. Please advise on of you believe he could have some type of fungus or other illness. Thanks in advance.

 

[Chinadog]

From the photos it doesn't look like fungus, I'm pretty sure its just his natural colour changing as he ages. I've had wild type Axolotls just like him that developed white or yellowish areas like that for no apparent reason, it never affected them in any way so unless he's showing other symptoms I wouldn't worry.
He looks very healthy to me.