Hi guys, I have a very old B+W filter skylight vertuget coated, which I'm using on my helios 44m. The filter is clear and looks fungus free under normal conditions and sunlight, but when I put it in a air-conditioned room... weird marking on the filter (it looks like fungus) start to form. It's probably due to condensation/moisture after removing it from the room. I can easily wipe the fungus-like markings away with a cloth and the filter looks normal again.
I checked online and it may be delamitation where the lens coating is damaged.
Anyone can help me on this? Is it fungus and will it spread to my current lens or the other lenses in my dry cabi?