A21M slight yellowing on bottom of LCD

[wogeboy]

Hi again:
I have a A21M that the screen looks OK..not as bright as it used to be, but fine. I noticed a slight yelow tint on the very bottom of the screen. Running from lentire lenght left to right. It's barely noticable, but there. Any ideas to what causes this? Inverter? Backlight? (or just slight burn on bottom of LCD?)

thanks for any input

14.1 "
P3 800