Looking to my collection i have been noticed that there are some marks on the edge of the game discs, like glue or adhesive of the discs squeezed out from the outer edge, for example this Xbox 360 DVD-ROM:
This is an example from a user with a similar case on my BD-ROM Xbox One games but is less visible; they looks like little bubbles of adhesive:
Source: Crop of original by BlitzDev54 via Reddit
I should point out that it is not as if it were the exception, if not rather the norm, the majority that I have looked at have said marks to a lesser or greater extent.
Is this early signs of discs rot? I have not found nothing similar to this.