Spotting on windows

Hi guys

Ive been cleaning windows on an old listed building (modernised) with our reach and wash system for many years now 

but we started to notice little spots on one side of what I thought was residual from trees around the property.

I’ve cleaned many windows with all sorts of stains, lime scale and everything imaginable

but nothing like this before. 

Ive used several different detergents on this property, fairy liquid, degreaser, and a few lime scale removers but none 

have removed these spots.

Has anyone encountered this problem and can recommend any products or ideas 

many thanks 

Got any pics ?

could always try unger rub out, or a tub of the pink stuff on a piece of old scrim and see if it will remove it but it’s labour intensive work. 

I think benz softwash sell something you can put in pure, it might help