That GH number indicates soft water (90ppm = 5 dGH) so for livebearers and shrimp I would harden it. Easiest way is with dolomite gravel if you can find it; it is a white gravel that slowly adds calcium and magnesium to the water; I use it in the filter, in a small mesh bag. A couple tablespoons lasts for months if not years. The benefit with dolomite is aq nice pH buffer too.
Second choice is crushed coral gravel, same process (bag in filter). This adds calcium only, but that will suffice for shrimp and livebearers. Doesnèt take much.