The LED Panel Light may appear light yellowing after a few month using, Because the physical reaction of PS LGP (light guide plate). The LED Chips will be pressed and broke due to thermal expansions and contractions of PS LGP, and plus with the quality of LGP and LED chips, it will happen with this phenomenon.RUNWIN LED Side-lit big Panel Light use stable PS LGP and reliable LED chips to avoid this problem better.And also We develop back lit big panel which can avoid such phenomenon more happened with side lit model big panel.