Mysterious gray/wavy patterns appearing all over new blinds

[Jeremiah Satterfield]

I recently purchased a duplex and bought the cheap China-made vinyl blinds from Lowe's (Project Source). I hung them up in both sides of a duplex. Within 3 days, this gray, splotchy, wavy pattern started appearing on ALL of the blinds in ONE side of the duplex. We scrubbed the blinds and the substance comes off a little, but not completely. Anyone ever heard of something like this??

Note: it's not simply dust from the house. We don't have any AC in the house yet (it has been hot/humid....but so has the other side of the duplex where the patterns are not showing up). I've called the manufacturer and they said they have not heard of it. I even called around to some air test companies and they've not heard of it either. My fear is that it's reacting to something harmful in the air. It is a very old duplex....built in 1905. But it has been fairly well maintained.

My worst fear is that that you was previously used for meth manufacturing. But this symptom on the blinds matches nothing I can find online around former meth-labs.

Anyone ever heard of or seen anything like this?