Gold fish changing colors

[Jazz.pliego]

First of all my fish turned completely white about 5 months ago and now his fins and his head are starting to look yellow
Can anyone help?
I have a 55galon tank with 2 gold fish( his is the largest one and oldest one too 4 yrs)
And 3 small tetras
Tested water and everything is in good condition

 

[Angellove78]

they tend to change color as they get older. Nothing is wrong with him. He's very pretty!

 

[Angellove78]

Or he could be losing scales. Sorry didn't focus on the fist pic.