You might want to check with local water control agency. I just used this website
Homepage - Thames Water - Contact us, pay your bill, tell us you're moving and entered a random but exisiting post code from N4 borough of London. It turns out the water there is hard. very. calcium content over 200 ppm is concidered hard and this area has 275ppm!
You might want to try something like fairrieanum whose natural habitat contains high content of limestone.
You can look up list of paphs that are found in limestone rich area in the wild.
Maudiae are naturally from jungle with slightly acidic soil I believe.
Many of the carnivorous plants live in acidic soil, and it's not surprising yours didn't do well.
I water all my orchids (many paphs included) but NYC tap water is fairly soft.
R/O system thing was very expensive, so I wouldn't try that just for plant hobby. You could look online for some low cost devise that removes minerals from your tap water.
Good luck!