I'm seeng this as well on my black dakota seats. i know this is not a high-line leather. i treat the seats at least monthly with 1Z Lederpflege. Mainly I see it on the passenger seat. 1Z is a good product. It's definitely not mold. I'm going to try leathermasters on it and see what happens. i will mention it to my SA on next visit though.
Auf Wiedersehen 12 550xi