The mould thing
Disclaimer: I haven’t and won’t be watching the film.
The mould thing is Uwe Boll letting his German preoccupation with “Stoßlüften“ seep into his directing choices.
German apartments and buildings aren’t really built with natural air exchange, so you “replace” all the air by opening the windows wide for a few minutes several times a day. There’s a stereotype that foreigners don’t know to do this, because it’s not always necessary in our countries of origin. Likewise, there’s a stereotype that “lower class”, poorer or I guess in Uwe’s case, sex workers, who he probably considers “lower class”, don’t know or care to look after their apartments, and therefore don’t lüften. Landlords also like to blame any mould on poor lüften habits, even when the apartment clearly has some structural issues and needs renovation.
Anyway, that’s my theory on the mould thing. I’ve been in Germany a few years as a (white) foreigner, so feel reasonably confident in this conclusion, but any Germans please feel free to correct me if I’m off-base.
Edit: grammar