

Black stuff on water fountain filter right after cleaning.
I just deep cleaned my petlibro fountain the day before yesterday and changed the filters. I went to change the water today and the white filter has black stuff on it. I have never seen this before and I have had this fountain for over a year. It’s the first filter from a new box. What is it?? Mold? Why would mold grow so fast when it hasn’t before? I am attaching pictures of the filter.