Hi all - I just received a new 27" iMac, and the screen quality seems quite poor. There is noticeable darkening and yellowing in the upper left corner of the display. Below is a picture of the screen taken in a dark room with my phone (the photo's brightness has been reduced to show the issue). Is this typical of the new iMacs, or should I send this unit back? My previous 2 27" iMacs (non-5k) have much better display uniformity.