[cypher]

Three is a really good age for a Russian ham, many don't live more than two years so Luna is doing well!
She is obviously showing signs of old age now though, if you haven't already you may need to rearrange her cage so everything is within easy reach & she doesn't need to climb or struggle to get to anything. Just make things easy & comfortable for her.
Russian hybrids often change colour quite a lot with time so the white spots may just be normal colour changes if you mean just her fur & not skin changes.