What's wrong with my Starburst Monti?

[muzikalmatt]

So I got this Starburst Monti frag in the middle of last week and it looks like it's starting to bleach. None of my other corals, including the other new frags I picked up, are having any issues. I tried inspecting for montipora eating nudibranchs and haven't noticed any, but I guess I can't fully rule them out.

My most recent parameters are as follows:

Temp: 76.8 F
Nitrate: 7 ppm
Phosphate: 0.04 ppm
Salinity: 1.027 (a little high, but I'm slowly bring it back down to 1.026)
Alkalinity: 8.7 dKH
Calcium 430 ppm

I don't have a recent magnesium measurement as my test kit has been acting up and I'm waiting on a new one. The "starburst" polyps tend to come out in the morning and then recede later in the day. The white patchiness started maybe two or three days ago and seems to be progressively getting worse. The spot it's in on the frag rack is receiving ~150-175 PAR so I wouldn't think the issue is too much light. It's also right next to my Jebao OW-10 powerhead set to Else mode, so I think it's getting good flow as well. I have another standard red monti cap in my tank that's doing fine, so I'm not sure why this one seems so unhappy. Any thoughts or ideas would be greatly appreciated. Thanks!

 

[muzikalmatt]

Let me know if you need better pictures and I can get them. I should have slapped on the polyplab filter to cut the blues but I was in a rush on my lunch break. Thanks again in advance for advice.