Sometimes it good to just let it be . Be it nsw or salt mix . If you have just a few corals especially only LPS then the water u have is good enough, do not change anything like add calcium or mg or increase KH.
Increase the salinity up to 1.024 and that about it.
The corals not opening up is likely due to your constant water change.
By the way , if u don't use rodi for saltmix , what do u use then? Tap water?