Is this evidence of previous mold on my endpapers or dirt?

On my Heritage Press Dracula. Whatever it is, it isn't much and it is only on the front and back end papers and only on one side of the endpapers. All the other pages in the entire book are completely clean and white. I took the white art eraser to it and only a little bit would come off. I also put the slightest amount of isopropyl alcohol on a microfiber cloth and went over the dirty areas. My towel was just barely damp before I wiped the dirty areas. Very little, if anything, came off and these pictures are what it looks like now. The book smells great and the rest of the book is beautiful. The slipcase is also clean and spotless. I also tried dabbing with hydrogen peroxide. I also sprinkled cornstarch over the dirty area and let that sit for 24 hours and then wiped it all away and used a white art eraser afterwards. I want to clean these endpapers up if at all possible. Is this book safe to keep in my collection? It's not that easy of a book to find and I want to keep it if at all possible. A user on facebook told me it looks like mold and to discard it. A few pictures in the links below:

https://drive.google.com/file/d/1pCByCxfegu5jeYGiI-2rW_OJDs0eIC7I/view?usp=shari...
https://drive.google.com/file/d/1pdHz0uZ0rI_UBrCbZLbckpmkYg7lIry4/view?usp=shari...
https://drive.google.com/file/d/1pQnVnBjn0ZFr2Ecf5v8znucAlHR-Q95E/view?usp=shari...

Curious. I would guess that, as these marks are confined to the endpapers, it is most likely that they were on the paper before the book was bound. Did you buy the book from the Heritage Press? If so, why not ask for a faultless replacement?

Hydrogen peroxide is an efficient bleach but applying an aqueous solution will surely distort the paper and leave you worse off.

Good luck!

>2 abbottthomas: I just bought this book used. This book was printed in the 1950s or 1960s. The seller tells me that they are the original owners of the book and that it was stored indoors for its entire life. To me it seems like evidence of previous mold/mildew. I wonder if this book will cause harm to the rest of my collection. This book is hard to find and so I would like to keep it if at all possible.

Because the paper doesn't smell like mold at all, I wonder if the previous owners had stored sheets of papers (receipts or notes) printed with non-archival ink inside the book. I can think of a few ways you'd get ink on both the front and back end papers, though I'm not sure the marking patterns support any of these scenarios.

>4 aspirit: maybe it is mildew instead of mold. Almost all of the old used books I have bought have a bit of that "old book smell" but none of them have any stains at all. The book in question also has a very slight old book smell but it's of the same intensity or less than all of my other old heritage press books that have no stains. After some other opinions on facebook I think it is mostly light foxing. There are 2 very tiny foxing spots on the textblock which are not in my pictures.

>5 RickFlair: well, foxing, perhaps. Sometimes, the glues used are slightly acidic and that can result in oddly shaped stains, spots, etc. appearing on the end sheets, especially on the paste-downs.