My dog...weird

As I was bathing my all white dog today I noticed something weird on her ears that I have never seen or noticed before...it's like they're turning black. I know it's not a hygiene issue because I bathe her very well but not more than needed and I tried to scrub at it to get it off and it's like her skin turned dark/black...almost reminds me mold..i don't understand. Should I be concerned?! I plan on calling the vet but I just wanted to see if anyone else has ever seen this happen on their dog and what it was???