What's wrong w/ our bro?

Mom's kinda worried about our brother Hitler. He is, or should we say was a tri-color goldfish (black/gold/white). Now he is all white except for an orange spot just behind his head on his back. We are all "feeling" fine, and have no health problems. Our home is the right size, is cleaned like it is suppose to be, and we are fed according to goldfish standards (twice a day/12 hrs apart). Dad thought maybe he was chlorine sensitive, but they treat our water like they are suppose to, and we are not showing any signs of the water being "weird".
Does anyone know is something is wrong with our brother, or are mom & dad worried about nothing???

***UPDATE***
Our boys are fine...we asked at the pet store and were told that some goldfish change color as they get older...even though they are all the same age/size, and that they never change back. Hitler is now ALL white, Roosevelt & Churchill haven't changed at all.