Until recently, I have used aquarium water for my tillies. That water is always run first through a Brita filters (other filters might do as well or better). I figure if it's okay for me to drink, it's okay for my fish. I change out some water up to 2x a week and set the "old/used" water aside to soak Tillies in or put in spray bottle to mist them. I now have only one aquarium (10 gallons) so less water is available (and it evaporates fast in my climate), but no fewer tillies! I still try to use aquarium water but have had to use tap water lately. This water has sat around for at least 24 hours to try to get rid of some of the chlorine. We used to have hard well water here in Albuquerque, but a few years ago began to switch over to using river water (due to running low on well water), so river water is softer. I have not yet noticed any problems with build up ("caliche"), but if I were to I'd probably give the affected plant a bath in pure filtered water or maybe rain water (if it isn't polluted or radioactive) and maybe gently rub to see if the build up will come off. I note in your sample picture, the plant has bloomed some time in the past and has a nice pup, so maybe some of the problem on the mother plant is age...? The pup looks vigorous and happy. I have one something like it, with the pup jutting out at 90 degees -- seeking even more freedom from mom.

I use exclusive rainwater, but the place I got them from probably didn't, and they were sitting in the water that had collected in the bottom of the plug tray wells. That pic is just one of four that I bought, and they all have the same thing on them. And as for species... the more I look, the more I think they may be kolbii? Anyone agree or have a different opinion?

Keep using rainwater and the limescale will eventually peel off. ... Species - I think it's one of ionantha long forms. Kolbii has wider base and more space between leaves.