I had the same "thing" a few days ago as well.

I was trying out a new hair product I bought and in the final render there were these kind of black spots all over the characters face and (new) hair as well. Areal (?) renders had the same spots at the same places again. Turning the camera and the figure a bit fixed it tho.

As I recently updated to SR 2.1 and never had this happen before, it made my suspicious. The renders I did over the weekend were all good again. So no clue, as of yet, what it caused it, as I was not able to reproduce the spots again in any of the renders.