Tri color help

[mevstheworld]

Well I got it at the beginning of the month, fine until now. Here's a shot of when I first brought it home.

It has been doing fine up until the past 2 days it has gone through RTN starting from the bottom. Yesterday I fragged it into 4 and seperated them from each other. 1 has turned ghost white(dead) and another one looks like it might be gone by tomorrow. The remaining 2 seem to be holding so far All my other SPS are doing great full polyps, encrusting, business as usual. Does anyone have any clue as to what could be the culprit? I had it placed high under T5's overdriven with plenty of flow. The frags I put lower hoping that would help. I just tested my water, results are as follows.
SG : 1.0256
PH : 8.3
Am : 0
NO2 : 0
NO3 : 0
Cal : 440
Alk : 12dKH
Mag : 1380
Temp : 78F

All of these stay very consistent, I've been documenting them from the 1st of the year and nothing really swings. Any suggestion??????

 

[pwoller]

I would be looking for something eating it at night.

 

[mevstheworld]

I inspect and explore my tank at all times of day and have yet to catch any fishy business going on, but that does not mean it does not happen I know. It just seems as if it no longer wants to live in my tank.... ALL other SPS are doing GREAT, just has me stumped. Thanks for the tip!

 

[Rouselb]

I have stopped RTN by fragging off like you have, and dipping in TMPCC several times over a week (3 times). I just keep the temp as close as i can. Any sudden change will just shock it more.

 

[mevstheworld]

Well, so far no more die off. Just the 2 remain. The only thing I did was frag and lower them from the light.

 

[mevstheworld]

Still doing fine, even starting to encrust ;)