Color Changing Chin

Hello - I have a standard grey male chin named Bentley who is 10 years old. His color has always been dark around his haunches and face but most recently his coat is starting to lighten up.

He seems the most healthy that I've seen him since I switched to proper pellets and hay. He eats about 2 tablespoons of Oxbow pellets a day, a good amount of timothy hay and sometimes orchard grass. He gets sticks and wood, has a large cage. He also gets out of cage time daily. He drinks about 4 - 6 ounces of natural spring water daily. His treats are organic rose buds and rose hips, about one a day.

He used to barber badly but now it's all grown in and his coat is thick and soft. So much more luxurious than it used to be. But I'm puzzled by the color changing.

Sorry this probably seems like a stupid question but I honestly don't know. Should I be worried about the color change? Do old chins get grey like old cats and dogs? I know he's not that old compared to some but maybe for him, (there's some history of improper care with previous owners and even myself until I learned better) he's aged because of this?