I recently purchased an out-of-print book from a retailer on Biblio. Upon inspection I noticed [green](https://i.imgur.com/DwXXBKd.png) and [black](https://i.imgur.com/pwAQ69b.png) smears on its bottom. Nothing on the face of the pages. No other stains to indicate water damage, etc.
Are either of these stains actually mold, and if so, how do I treat them?
by Py687