before you do anything, please figure out the parking spot and check if there is any renovation work like painting, sand blasting or ac installation has been going on around the place.
and OR
someone has used BATTERY Tonic around the vehicle under envious feelings.
am asking this for the fact we suffered some pin dropping spots over rear screen in 2016 for a new un registered corolla parked under open sky. serious investigation revealed ac outer unit diagonally upward had a flash gas purge which caused screen to appear rain dirty. It was cleaned by 3S with some detailing compound.