When siding is washed, one is suppose to start from the bottom and work their way up the wall. If one was to start at the TOP instead, the cleaning solution, or whatever is on the wall, washes down and 'streaks' the siding. By starting the job at the BOTTOM, the siding is clean and wet, and there really isn't anything for it to 'streak'.
First, I'd ask what they used in their water for a cleaning solution. If it was just water, it could still streak but a cleaner should get rid of it. IF there was a cleaning solution, find out what it was. Then ask, or mentally recall, if they start at the TOP or the BOTTOM. It's still possible that cleaning the siding with water mixed in a cleaning solution will fix the streaks.
I wish I had more to offer, other than repainting the siding. My best to ya and hope this helps.