Substance building up on Vinyl blinds within hours of putting them up

[Frank Germaine]

I recently was replacing vinyl blinds at a property and noticed within hours of putting them up, they seemed off colored and splotchy. Thinking it was just the specific blinds I bought, I returned them and purchased different blinds from a different company. When putting he second round of new blinds up, I made sure they were white and left the house. I came back a few hours later and once again the white blinds had turned gray and splotchy. Whatever this substance is that is collecting on the blinds, it does not come off easily. It is not coming from the outside since the windows are closed! It is an old house (1910's) and I am worried that the substance is either in the air, or the blinds are reacting to something in the air. I will post a picture when I can figure out how to on this forum. In the meantime, any ideas on what is causing this? I am concerned! Thanks!

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