It seems that I found the root cause of my stn rtn issues. I had a jeabo UV sterilizer and the inside of the sterilizer abs was being disintegrated by the UV light. I've been doing water changes like crazy for months and lots of carbon like 5 gallons of carbon I've gone through yeah and it just kept progressing until I decided to clean the UV sterilizer and noticed it was dissolving from the inside
Ever since I removed that sterilizer from the tank the corals have begin to recover the few that survived and I'm seeing calcium and alkalinity consumption go back up