Sounds like my grey dapple...now I know that grey's turn white over time but Dumas always looks best in spring. Now that it's November, he's got his winter fuzzies comming in quite nicely. I notice it in the areas you mentioned first, then he starts to fuzz into a winter white-ish full coat.
I think it's normal and nothing to worry about.
Be strong and courageous, and do the work. Don't be afraid or discouraged by the size of the task, for the Lord God, my God, is with you. He will not fail you or forsake you.
1 Chronicles 28:20