Definitely could have come from the new fish. When your friend gets home from work, I'd go test his water and see what his readings are.
I treated my tank with Parasite Clear for two days. It's a product that's made by Jungle, and can easily be found in your local grocery store. With large tanks you'll more than likely need 2 to 3 boxes of the stuff. It's one tablet for every 10gl. After I treated the tank, everyone started acting normal again, and all seems to be well. The only one who was showing symptoms of a parasite was my Pictus Cat. But the Oscar, the Dempsey and the Pleco all pooped out a bunch of white stuff, and then went back to normal. lol