Why would you try to change your pH value for your fish? It really doesn't matter, unless you have some crazy high or low pH values, but that would point to other issues in your tank.
If your other parameters are within the recommended ranges, your pH will very likely be fine for the fish in your tank. Most people do not alter their pH at all, even in tanks with stony corals, let alone fish-only systems...
Looking at your previous topics, did you use edible salt? Using a salt that only contains NaCl and dissolving that in RO water, will give you saltwater without any pH buffering capacities.