Brown stains on awning window

Lindyloo
Lindyloo Forum Participant Posts: 21
edited April 2015 in Parts & Accessories #1

Forgive me if this is already covered somewhere.  We have just opened up our awning, with a view to getting it ready for sale.  However we have noticed there are some brown stains on the windows.  The awning is only 4 years old and has always been put away
clean and dry.  Does anyone know how to remove these stains please?