Hey Toad, I'm new here but I own 4 goldfish (carp) that I raised from feeders, they're about 2 years old now. All 4 started out gold, but one about a year or so ago began getting patches of white scales, and eventually he turned completely white. He's still very healthy (except for a nagging lip injury due to him feeding off of things on the gravel in his spare time) and active, doesn't seem to have affected his health at all.
Hopefully this is the same for your fish! Just keep an eye on his behavior and take note of/research/ask about anything that seems strange!