SONY PDW_F350 filter galss unit problem

hello to all
my name is Andrea and use the cameras f350 for many years, I possess five.
lately I see the images from the cameras to change the definition and even color, until a short time ago by putting them in the preset I needed a few corrections to make them equal. jo discovered a terrible thing: 1-479-899-11 FILTER UNIT, OPTICAL is stained as if it were neckline.
are final, desperate because checking other cameras I've noticed that you begin to stain the other units.
spare parts cost a lot.
I know for sure is that optical glass, with a kind of filter, UV protected, because the ccd 1/2 inch of the camera are very sensitive.
advice and assistance
I am attaching some pictures

thank you

Andrea Pucci

https://www.dropbox.com/sc/x7rza1ya8cmgf5l/AAAnQvUiyBhvsg7dEdf9GI37a

https://www.dropbox.com/sc/h7nffkbudl4bfs4/AADOltIBuh6xXdQDvwaUzh7Ra

https://www.dropbox.com/sc/ej7oq7cmzaxk424/AACzy0XxLseQkuarA_-cmpYla