Technically all freshwater aquarium keepers need... IMHO.
If math in my head is right your tap is around 9dGH. Pretty hard.
Does water report give sodium levels?
Thing is java fern, moss, hygrophila should do ok in your water. Thereís something else going on here, I donít think the L. Repens should be dying on you.
What kind of filtering do you have on your tanks? Can your run a big bag of carbon on one them?