I just noticed that there is a faint yellow tinge on the lower right-hand corner. Its like the a quarter of an ellipse with the center being the corner. Right now it seems to be go an inch to the left of the corner and an inch up.Since I have been leaving the monitor on overnight, could this be burn-in from the yellow sleep light at the corner? I can't seem to get rid of it, and it's not dirt. How do I get rid of it?