Be cautious on how much advice you take. There are 1000 things it could be and you'll get a lot of different answers. I highly doubt it's po4 related by your numbers, and adding something like gfo or carbon dosing may make your unknown problem worse with those numbers. Have you done an ICP test?I'm honestly confused at this point my tank is clearly having some issue and i can't put my finger on it. I can't keep any sps at all they all die within a week or 2. All my parameters are good.