I think Teddy and London have it too. I've been wondering what it is and was even going to post a thread but then read this one and it sounds like the descriptions you guys gave. It looks like dirt but it doesn't wash off and it's on their lower tummies, near their privates. I asked the vet and she didn't know
So i guess it is clogged up pores, does anyone have any pics of what it looks like to be sure? They just appeared out of nowhere!