This was copied from their website…did you try what the recommended before having your house washed?
Not only can ABC Seamless steel siding stand up to the elements, but it can provide top protection against:
Impact Rotting Insect and rodent infestation
It’s low in maintenance, too. You won’t have to scrape, paint, or pressure wash your ABC siding to keep it in pristine shape. An occasional rinse with a garden hose is all that’s necessary to revive its striking, like-new appearance. It comes in several attractive options, including a log style and a traditional board and batten style.
try emailing them: email@example.com I would send them a picture and maybe they have a simple solutions or have seen this before.