Discoloration on the screen

[g10]

I'm not sure exactly how to explain this but this has happened twice so far and I need to bring it in for a swap again.

On the screen I have what i can only describe as an oil spill on my screen. It has that funky look oil does when its floating on water. It's a rectangle shape over part of the screen. Wondering if anyone else has had this issue? I mean its happened to me 2 devices in a row now so I would hate to assume my luck is that good!