Ok so picked up a new custy a few months ago as her old window cleaner seemed to be leaving faint scratches on the glass now I've been doing them for these past few months and everything has been fine until today where she noticed one or two faint new scratches?????? I always make sure my brush is clean and always run my hand through it to make sure nothing in there so why are these coming up I also do these windows very carefully as there very tempamental cheap PVC with those nasty stick on PVC middle frame bars.... But she can't get my head around it is it something I'm doing no one else have ever brought this to my attention please help