I bought an ACD second hand and it was in great condition, no dead pixels or smudges. After not using it for one day after a week of heavy use. There is a weird smudge on the display. It isn't too noticeable but is such a bummer as it was fine for 5+ years and now this. Is there any way to remove or fix this? I tried scrubbing it away but nothing. Here's what it looks like, right in the center of my display..