I have white marks on my windows

[Martyn]

You have mentioned that after a few cleans, this should stop showing. The cleaners have claimed that it is done every 2 months, so is it likely that the windows have not been cleaned, or not cleaned/rinsed properly if this is the case?

2 monthly is not frequent enough, needs to be monthly to keep it at bay.

 

[Stevieboy]

Great answer. When the inert gas which is commonly nitrogen leaks out the capillary force between the pains creates condensation and causes milky water Mark's which look awful. Something to be mindful of when meeting new customers and explaining you can't polish a turd 

Argon not nitrogen.