black mold

I had made another thread asking for help about some of the strange behaviors and symptoms I was seeing in my 2 boars the past few weeks, which goes a lot more in depth on everything that’s been going on. Since that thread, my quarterly inspection at my apartment done by maintenance found what...

Hello, the mouth peice to one of their water bottles looks black, or tarnished. My grandmother thinks it's just marks from them biting it, but it doesn't look like that to me. It doesn't look like mold either, but I'm definitely no expert. (Sorry if the pics are a little blurry!)