Help Discoloured white Tab back.

[gaugerer]

The white plastic on the back of my Tab has become discoloured with a faint pink pattern. I've had it in a leather holder that I bought on Ebay which has a black cloth lining which doesn't appear to have caused the problem. Has anyone else experienced their white back becoming discoloured?

 

[gaugerer]

I have left my Tab out of my leather case and the discolouration on the white back seems to be getting slightly better on it's own.

 

[gaugerer]

The discolouration on the back of my Tab continues to improve the longer I leave it out of a case and is almost back to the original white. This leads me believe that that the discolouration was not deposited on the Tab from the case but due to internal changes in the white plastic, possibly due to heat. Though the Tab never felt particularly hot especially compared to my Nexus One which got extremely hot when used as a Satnav in the car.