Discolouration from heavy rain or pooled water on coatings is called ‘water whitening’. This usually occurs when rain falls and pools on the surface within the first couple of weeks after application, while the coating is still curing. Full curing takes 7 days in ideal conditions but can take longer in cold or wet weather.
Good news, water whitening does not affect the integrity of the coating or its exterior durability. It might not look nice but it will usually go away once the surface dries out and will stop happening once the coating has fully cured.