Is this a mold infestation?

We recently moved into a new apartment and noticed these black streaks forming inside some of the bathroom cabinetry. Oddly we noticed the same phenomenon on some of our cookware in the kitchen. Does that look reminiscent of mold?

https://preview.redd.it/ggatx2gmxf2d1.jpg?width=3024&format=pjpg&auto=webp&s=a845b6aacfd31a1b348d6d9ba8120aa20020748a

https://preview.redd.it/ysi0w2gmxf2d1.jpg?width=3024&format=pjpg&auto=webp&s=f891542450b61c1655b00fc511ac7c51976d9355