Thank you for your advice. Yes, its internal I guess. I wish if any DIY technique will look new. Thanks againOof. Not to crush your expectations, but I doubt that they'll look good again. That's basically the plastic cracking, and that's inside the light. Mine have that too, and its not repairable. Yout do seem to have some oxidation as well, which can be fixed.
The best method I have found is to sand and polish the lights. wet sand with 1000 grit, then 2000, then 3000. THen, polish the lights with an electric polisher and polishing compound. You can go by hand, but it takes for ever and doesn't look as good.
As I said, you'll probably get less-than-perfect results, but you'll likely still get an improvement (I did). It's worth a shot.
Also, if you don't have a polisher, there are kits that attach to your drill. They are a bit more expensive, though.
Thank you for your advice. Yes, its internal I guess. I wish if any DIY technique will look new. Thanks again