Check the website of your water authority, the GH may be posted there, as general hardness or total hardness. They may have the pH too, which will confirm your tests (and pH can change in an aquarium, it is good to know the source water pH and GH to be certain).
Leaving the parameters (|GH, pH) for the moment, if rummynose are suited, you must get more of them. This is a shoaling fish (like all tetras) and it needs more of them. An additional 7 would be minimum, for a total of 10, but 12 in total even better. This is very important with this species.
The zebra danios would be best left out, especially with the sparkling gourami, but I realize you already have them. Maybe the store would accept them back in return for some of the rummynose? Just a thought.