Silver Schnauzers hair turning black - why?

by Vanessa Pagan
(Humble, Tx - USA)

Why is my silver schnauzers hair turning black? She has always had a pretty, silver coat.For the most part, she still does, however, there is a dark spot of hair on her back that just seems to have gotten larger with time. When she's dirty, it's very oily, and once we bathe her, of course, it's nice and fluffy again. Just curious ifbthis is a grooming thing, or because of her age.

Thanks for any information!!

V. Pagan