Mine looks fairly similar. Do you find if you move your head down lower that the yellowing is lessened? For my 2012 27" iMac it is. It's viewing angles causing most (not all) of the yellow.
Anyway, I'd say that's not too bad considering. If everything else is in order, I'd keep it, but that's just this nutter's opinion.
Anyway, I'd say that's not too bad considering. If everything else is in order, I'd keep it, but that's just this nutter's opinion.