Hard COral Diseases?

[Navarchus]

Hi
Usually a change in alkalinity may cause that problem. What is your alk?
Another direction is a change in salinity or in temperature. In my experience some folks damage their system during water changes without proper equalization.

I have also noticed your ca is on the low side and you don’t have an ALK and MG test results. If you can provide dose it will help diagnosing you problem.

When you touch you sps corals do they brake easily?