hedgehogsdad said:
I had my car washed last weekend at a local hand car wash.
This is your problem.
They will have used wheel acid to clean the wheels, or alkaline traffic film remover on your cars.
These products bring the dirt off really quick and leave a nice shiny car, but the acid / alkaline continues to east away at your car accelerating corrosion.
Your discs are very susceptible, as are alloys - any paint damage and your wheels will be bubbling up in short order.
Wash any car you care about yourself by hand.