Nokia Lumia :: Marks Underneath Screen Of 820

Ive had my NNokia Lumia 820 approx 4-5 weeks and though Ive got no software problems with the phone, about a week ago, I noticed what looked like smudge marks on the underneath of the screen, at the top under the speaker and in the bottom left corner of the screen, about a third of the way up. I just happened to notice in the daylight today and have noticed that the marks are growing in sixe, especially the one in the bottom left corner, nearly halfway across the screen. I suspect its a build quality issue as Ive never had this issue with a phone before.