Hi. Have a Mid-2012 Retina Mac, with active AppleCare. Had the motherboard swapped-out on it a few months ago, and everything has been working great since then. However, a week or so ago, I noticed this white-blob-looking thing on the bottom-left corner of my screen anytime there was a white or gray background displayed. The blob doesn't show up with any other color other than white or gray...but still, it's obvious that something is wrong in that part of the screen. It's very faint, but now that I've seen it, I know it's there. What do you guys think...is this worth a trip to the Genius Bar for me to request a repair, or will they tell me to pound salt. Also, anyone else had this issue, and what happened? I don't want to complain about every little thing, but it doesn't seem normal to me, and I'm worried it will get worse if I don't. Appreciate any insight you guys might have. Thanks!