Hrm seems a bit weird as your parameters are all inline, has anything changed recently? We're the corals ok before and now having trouble or steady decline?
Also wondering about your dosing and your WC scedual cause most time new tanks don't have much demand for dosing so it isn't. Needed till corals start to use more of the calcium and Alk up in between water changes
If say start with some easy things like a water cjange and maybe some more frequent ones for the next bit see if that helps.
Also are you feeding anything to your corals reef roids frenzy or anything like that it could be that your water is too clean and your GFO and carbon are stripping the water of all the nutrients before they get to use them
That's my 2 cents for now
good luck