what you guys mentioned are temporary solution. Plastic has a layer of protective coat to proctect the plastic headlight and this coat get thinner and eventually gone over years which you will end up a yellowing headlight, espeically top portion for EK with direct sunlight on it.
You can sand it off and buff it back, but it won't last since the protective coat is gone.
There are several headlights restoration kit out there and basically what they did has atleast 3 steps of chemical application, first remove the last layer, then buff it back, and last apply the proctective coat on it to seal the headlights.