Maybe since you got the car used there's no real way to answer - but we've noticed where I work that many kinds of hard plastics will craze if they come into contact with alcoholic solvents (ethanol, antifreeze, etc), unless washed off within a few seconds. Maybe that happened at some time in the past.

I also had spotting and damage on the dash of a car from using "Armorall" and not wiping it off right away (within seconds). The damage wasn't really evident until the next day under sunlight illumination - then it was very obvious. Don't know if that would affect the lenses or if someone in the past might have used it or something similar on your car.