Tissue loss, should I frag out?

[a.browning]

I have had a poccilopora for about 2 months. It only had a few branches when I got it and has grown extremely well. Last week, overnight, one of the branches completely bleached out. All other branches looked great so I let it be. Now another branch has bleached. I'm not sure why, I haven't changed any parameters in the tank and there were no obvious reasons why it would start to bleach.

Will each branch die off since a couple have now? I had planned to frag out the good branches in case it's started a mass recession of tissue. If anyone has better advice, let me know!

Water Parameters:

Calcium: 460
Alkalinity: 9.15
Magnesium: 1340
NO3: 0
PO4: .01 ppm
Ph: 8.2
SG: 1.025

Water is tested with salifert, P04 tested with Hanna P04 meter, and SG tested with refractometer.

Tank info:
55 Gal - 2 years old
SRO 2000 skimmer
Aquaticlife 4-bulb T5 fixture with ATI bulbs
Coral about 3/4 way up in the tank

Here is a picture of what it did look like:

What puzzles me is that I have literally done nothing but water changes, demands are met with Kalk in my ATO. Should I frag the good branches or let it be?

Thanks

 

[maxx56dog]

I would let it be, watch the coral and if it seems that the "bleaching" is spreading than frag the remaining colony and save what you can

 

[toothman]

If my phosphate were .01 I really would be excited because I would know I could feed my tank more food. More food equals more growth. I think most reefers really under feed their tank. More food generally always helps. As does a water change. It could also be that frog spawn sending out a sweeper.

 

[a.browning]

Thanks for the suggestions guys. Although it looks close, the frogspawn is about 4" away, camera angle I guess. I'm sure it could have 4" sweepers but I've never seen it happen. One thing I thought of, I replaced 2 of my 4 ATI bulbs 2 weeks ago, and then this started happening 1 week ago. I did not acclimate the new lights since I only replaced 2 of the 4. Could this cause the damage? I will check if its bleaching or tissue loss next time I'm home.