I posted a link a few pages back related to Freon poisoning (the coolant in air conditioning). Bacteria and toxic mold can also build up inside the A/C. I'm not sure if this applies to larger more commercial units or "central air" type systems? I also don't know if the cases of Freon poisoning came from exposure to the liquid itself or from inhaling toxic, bad air.
If it were poison from food or a faulty AC unit wouldn't that have been discovered by now?
@GoBuckeyes IIRC the skin turns bright pink/red due to oxygen levels. I believe cyanide causes skin to take on a blueish tint from lack of oxygen.
You'd think the moment either of them had these symptoms they would have called 911? Not gone into separate rooms.
@chimpface Appreciate your explanation. I went off thinking maybe the sisters were mixed up in some dangerous business that potentially led to their deaths.
I agree with the last post. In terms of two sisters being somewhat isolated and dependent on each other it would be easy for them to fall into some kind of "shared delusion" or to feed off/into each others fears. Between the two, there must have been one that was more dominant. Isn't that typically the way with siblings?