Display blotchy and flickering

[MikeLip]

It's hard to describe, but where the colors used to blend smoothly now they are all blotchy. Areas of blue, for instance on the standard wallpaper sky, have dark areas which are edged by pixelated areas. Almost like running Windows in 256 color mode. I tried a recover but nothing. The tab was just sitting for a couple of weeks and I came back to this. Everything works but it looks awful and the blotches flicker. WTH happened and can I fix it?