What makes Favites corals sulk?

[Rockster2599]

I have a 2 favites corals at either end of the tank but they have both (over that last week or 2) started to look peaky. They have lost colour, the tissue looks stretched tight over the skeleton and some areas look like they are receeding. I even moved one higher as I thought light may be an issue but if anything it looks worse.
My levels seem O.K?
SG 1.025
pH 8
Kh 9.3
Ca 420
Mg 1320
No3 1ppm
P04 0.04 ppm
I dont think it would be light or flow as they started to sulk at about the same time, the only things that I can think would be coincident are a slight raise in temp or my phosphates lowering (used to be 0.1, I have done this with rowaphos and my algae scrubber has taken off so I am phasing back my NoPox usage). I wouldnt have thought either of these would make a massive difference? I dose red sea A and B every 2 days.
Any advice appreciated as I think they will fade away without assistance.

 

[organism]

If your phosphates lowered too much too quickly that might be an issue, which is likely considering combining a carbon source like NOPOX with phosphate removal media can be very problematic and strip too many nutrients from the water at once. It can also make the water clearer which gives them more light causing them to burn. I'd move them into the shade and feed them until they start looking better.

 

[Rockster2599]

Cheers bud:thumbsup:
What would you feed? Ive never seen a strong feeding response and Ive had them a year.

 

[organism]

I would powder some pellet food, soak it in tank water for a few minutes, turn off all the flow and then lay it on top of the corals with a pipette or something. Just let them sit for 20-30 minutes and chances are they'll open up and eat

 

[Rockster2599]

O.K. I think I have found my suspect, I've just disassembled my MP10 and the ceramic shaft is cracked and rusting.