A PC rainbow acro on decline, what could be wrong based on this pic?

[2Wheelsonly]

I have this pc rainbow acro; it's near the top of my tank under radion G4 pro's. The acro is about 10 inches below the water line and my G4 pros are about 12 inched above. I have 5 of them above my 96x30x24

Params:

300 gallon with alot of flow (2 mp40, 2 4000gph mover, 1 gyre 150, vortech m1 return pump)
Mag: 1320
Calc: 450
Alk: 7.1 (stable)
pH: 8.2 day 8.0 night
Salinity: 35ppt
Temp: 78 (stable)
Potassium: 400
no3: 10
po4: 0.06

I dose acropower once a week.

Here is the coral, it has a few vermitid snails around it that may be "hurting it" as i'm still not sold those suckers don't affect the health of SPS. There is a white patch that looks like dead skin rather than bleach and the tips seems to be fairly damaged.

Based on my nutrients I can't see them as starving, if it was too much light wouldn't the entire thing be bleached?

 

[Ocelaris]

How's everything else doing? What phosphate test are you using? I basically have bleaching down to alkalinity and phosphates. If nothing else has changed, I would monitor those two every day for a week. Do a water change and fresh carbon. Feed heavy for a few days. It will take a few days for things to turn around, my thoughts are more nutrients are usually a help, fluctuations in alkalinity can also be a issue. My alkalinity went from 11 to 10 and my canary coral is withholding its polyps in response. It's back up now, but it'll take a few days for it to respond.

Sometimes there are corals that are warning signs for others. My pc rainbow doesn't seem to be that sensitive though.

 

[2Wheelsonly]

How's everything else doing? What phosphate test are you using? I basically have bleaching down to alkalinity and phosphates. If nothing else has changed, I would monitor those two every day for a week. Do a water change and fresh carbon. Feed heavy for a few days. It will take a few days for things to turn around, my thoughts are more nutrients are usually a help, fluctuations in alkalinity can also be a issue. My alkalinity went from 11 to 10 and my canary coral is withholding its polyps in response. It's back up now, but it'll take a few days for it to respond.

Sometimes there are corals that are warning signs for others. My pc rainbow doesn't seem to be that sensitive though.

Thanks for the response, it may be my alk then. I have been having to go out of town alot for work due to some end of year projects and my gate valve for my vertex calc reactor constantly gets clogged. I try to keep my alk at 8.0 but recently settled to 7.0-7.2 where I can keep it more stable. I think that has upset my corals. I think it's time for a peristaltic pump.

 

[Ocelaris]

I would say for certain then alk swings. It's basically the barometer for everything. I'm not convinced it really matters what your dKH is between 7 and 12 as long as it never varies. I gave away a huge colony of pocillipora, so I droped my alk/calcium assuming it would be consuming some, but I went too far, and my alk dropped. So now I'm measuring every other day and it's been stable back where it was at 11.2.

All your other parameters look good, and if you can attribute it to alkalinity, I would just go with that theory.

 

[Salty1962]

As mentioned, how is the rest of your tank? Does your livestock due ok with the Dkh @ 7.1? Is there a reason for it being that low?

 

[Lazys Coral House]

7.1 is really low. I would loose tissue on quite a few corals if it got down that low in my system.