ouch, the worst thing you can do is use lacquer thinner on fragile old plastic, I'd use some 1200 or 1500 or 2000 grit sandpaper with water ,sand in one direction for a minute or two depending on how bad is discoloration and use 3M Perfect-it II Rubbing Compound on foam buffing pad at lowest speed, they will look like new and most of the pitting from over the years will be gone as well