Question on glue

I’ve been offered a very fair price for the autographs below. I reached out to the seller to determine if glue was applied directly to the back of the pages. The seller responded that indeed glue had been applied to the back but was an acid-free type that won’t affect the paper or autographs.

In looking at the photo below, I suspect that some other type of glue was used previously causing discoloration of the pages that can be seen especially on the bottom right page.

Am I seeing things?

Jason