The iMac has 2 small (less than an inch) darker smudges on the screen towards bottom left corner. Really only visible on white background. I thought at first it's surface dirt but it's in the glass. I will be opening up the iMac to upgrade to SSD, is there anything I can do to get rid of these patches? I would post a pic but my phone camera captures lines on the screen which make the patch hard to make out.