No information posted so likely impossible to help.
That being said, I see a new tank which parameters can fluctuate widely, all corals hate changes.
If you can give some tank history, size, length of time since cycle and current parameters, maybe Imcan be narrowed down.
65L ive only measured nitrate and nitrite since i have no idea how to use the calcium tester and i dont have an alkalinity tester ive had the tank for about a month now and this isnt the only bad thing my xenia is also dying