Gray cloud across screen

[vegascats777]

I have a 42" LG TV that is only 3 yrs old. Recently when the background is light, ie sky, there is a gray cloud across the screen. What can that be?

 

[ElectrO_90]

That's as clear as mud... please upload a photo and show what you mean

 

[vegascats777]

That's as clear as mud... please upload a photo and show what you mean

The problem doesn't show up on a photo. Thanks for your snarky answer. I'll ask a professional.