[bigbadkahuna]

When you run your finger nails over the lenses, you can feel roughness. That is deterioration of the plastic itself. You can either use a chemical strip, like any of the specific for plastic polishes, but normally if it's too bad you need an abrasive.

Wet sanding with 1,000, 1,500 and 2,000 is best. Go in one direction using a sanding block, then buff with plastic polish.

If you want to preserve the finish, buy some of the plastic overlay stuff cut to fit your lights.

Bottom line is you've got to get the deteriorated outer layer of plastic off.

Good luck!