Wickback?

I cleaned this off white berber at about 350psi and it looked great when I was finished. These pictures were sent to me by the customer about 24-30 hours later.

There was a lot of construction dust that I vacuumed up prior to cleaning and they said that the pad looked good (it was pulled and relaid because they added a few partition walls)

I didn't leave any fans going after I cleaned it and I'm thinking that is what caused the problem.

Any thoughts?