Discs coming out of PS4 with little circular smudges on edge of discs

[klauswhereareyou]

I've noticed a weird thing that just started happening recently with discs played in my PS4. After playing them I've noticed after ejecting them that they are getting little circular smudges near the edges of the discs (on the bottom). They are not there before I put them in, and sometimes there are only one or two smudges, and sometimes there are several. I'm not touching under the disc at all so it's not coming from my fingers as far as I can tell. Has anyone had this issue before? Is there a recommended Blu-ray player cleaner that I can use if it's an issue of the inside of the disc drive being dirty (the out side seems to be okay)?