ALDEVAUX

Michael, I am not very familiar with the cultivation of jabotica, but from information in the web they do not seem to like alkaline soils. Since you say your tap water is hard, it means that is it alkaline and could cause the browning of leaf tips.
On the other hand, if your tropicals are healthy using the same water it means that they tolerate the high pH but are not disturbed by other chemicals in the water. Normally, tap water, unless it contains excessive amount of toxic minerals should be safely used for indoor plants except those that do not tolerate the high pH.
In the case of your jabotica, you can try using an acidifying fertiliser like "MIRACID" instead of using distilled water, which of course is o.K. for your plants, if you add to it a complete fertiliser containing minor elements.
Maybe someone with some experience in the culture of jabotica can give you other usefull information. Good luck.