Unknown cause of polyp recession. Help!

[DeLegge90]

My pocillopora has not been doing well recently. I had it in the perfect location with moderate to high lighting/flow, and it did very well for the past three months that I've owned it. Now I can see exposed skeleton in places that weren't there. And when trying a dip treatment, I noticed lots of polyps leaving the skeleton and floating around in the water. No signs of pests/parasites upon visual inspection. I'm guessing I'm having an issue with nitrates or phosphates, so I will test parameters tonight (unfortunately, all i have is an API test kit which I know to give less than accurate readings sometimes). Meanwhile every other coral I have in the same tank are doing wonderfully (torch, acan, hammers, zoas, xenias, gsp).

 

[JustAnotherNanoTank]

Have you changed any equipment or changed out any carbon or added GFO recently?

 

[Ike]

Also... What are you dosing? Looks like nutrients might be too low just judging from the pale coloration of the corals, but not enough information for anyone to really take a good guess...

 

[kireek]

My first guess would be something to do with water parameters. Maybe something changed suddenly?