19 is super hard! But I feel your pain my old house was 19, I'm now around 13 after I've moved which gives more options.
At 19 your livebearers will likely be ok, but the others may have shorter lifespans than they would in soft or neutral water. In harder water, fish found naturally in softwater can develop essentially kidney stones that will shut down their kidneys etc etc as their bodies cant process the additional elements in the water.
Your Tetras are not a terrible choice, the Black Skirts are so commercially bred it might not be too sensitive to hard water. X-Rays have a huge distribution in the wild so do start to reach coastal waters which are typically harder and Buenos Aires Tetras are quite closely related to Tetras found in harder water in Central America (though they are from South America in softer water) also an albino strain will be many generations deep in captivity so could be more prepared for some hardness, though likely not 19.
It does seem like you are losing quite a few fish so if you are open to it we can probably suggest some better options as a 120g tank you have loads of options - just a few quick ones, Central American Cichlids, Tanganyikan Synodontis Catfish and Rainbowfish would all do great in here. Yellow Panchax, a couple of Barb species come from these kind of waters. Lake Inle is an interesting hard water habitat too, Thick Lipped Gourami, Emerald Rasbora, Rummy Nose Rasbora all spring to mind so there are great options out there. Or if you ever wanted something totally different Malawi Cichlids, Peacocks or Mbuna would be great in water this hard.