Just something to double check.
There are some ventilation holes on the back that will sometimes allow light to enter from the back and cause some weird looking blobs on the image on the front side.
If you're using a back light or have light otherwise behind the display, it may be causing this event.
I had a Pioneer plasma for several years before getting the 65VT50. Since I don't like distortion, on occasion I'd run a program in 4:3 aspect ratio. I guess it was the accumulated hours in doing that where the far left and far right areas where the black bars were located would be more blue than the center area. (not yellow). So now, with the 65VT50, I'm careful to zoom in or use the lit side panel feature on my bluray player.
Something else that I recall. During the first few hundred hours, it seems that the outside edge had something of a lighter shade than the rest of the screen. It eventually went away.
When did you get your display and was it new when you got it?
Samsung 64F8500, Panasonic 65VT50, Oppo 95, Tivo Roamio for OTA, Dish VIP722, Marantz AV8801 preamp, Rotel Amps, Atlantic Tech 8200 speakers, Seaton Submersive HP, Calman 5, Chromapure, Accupel DVG-5000, VideoForge HDMI II, i1Display3pro, i1pro2, eecolor colorbox.