Strange marks on my iMac 27" screen
So, I just discovered some strange marks in the lower corners of my iMac 27" screen. The computer is almost exactly one year old now. They are not dirt, I've tried cleaning the screen but they seem to be "behind" the outer plastic. They are mostly visible on light areas. Attached image shows them on a light grey plain area. Any ideas what they might be and how to get rid of them? I've got similar but not so apparent marks on the lower right corner as well.
iMac 27", macOS 10.15