[RossBMWZseries]

I wonder if the shop that built your custom lights perhaps didn’t seal the lights correctly. If the yellowing is happening from outside, I recommend Meguiar’s heavy duty headlight restoration kit. It did wonders to my 328i. It was recommended to me by another forum member. That kit comes with a sealant. If you prefer, you can get the Lamin-X clear film for that extra protection. If, and I mean IF, the yellowing doesn’t clear up to satisfying standards, you could always get a lamin-X tinted film. Same protection, but the darker tint will hide the yellow haze as well as give it an aggressive look. Worth a shot