Hello again!
I feel like you do way too much with your tank and water before having any real answers about your parameters.
You need to find these out before getting any fish.
You must have spent a fortune on fish so far and I feel that the ones you bought are not at all suited for your water if it is hard like you mention:
You purchased mostly very soft water fish which will suffer in hard water.
It can depending on the types of wood and or rock you add. Plants however? Not sure there.
But unless you went out and specifically bought items to lower your ph...it probably hasn't changed. The wood and rocks that I've added in my tank have had no effects on my water, or my many plants.
You should definitely find out what it is thats "softening your water".
I had this issue when I first started as well.
I live on a private well and my water was on the harder side (well a higher PH) when I started but eventually became soft.
Long story short. My well is extremely acidic and soft. It has a zero KH (zero buffering power), so even after running thru my "softner" which is crushed coral and actually hardens my water bring my PH up....it eventually falls back down to a low PH GH because of the zero buffering abilities.
I don't understand this reasoning at all...maybe someone else will.
But I'm pretty sure all of the soft water fish that you've chosen will not appreciate salt added at all.
If I were you my fist step would be to buy myself test kits (tubes, not strips) and learn the proper way to test and get yourself the correct numbers on your water.
Also learn about what's buffering your water (softner) and what exactly it's doing to your source water.
Then you can go from there