seriatopora dying

[Keramio]

I noticed in the past week that my seritatopora calliendrum started to develop white spots from the base slowly dying off upwards. I would like to know if there is something I can do? I am not really sure what causes it. My parameters are pretty stable. And I have had this coral for about half a year now. No other coral shows any problems. Even my Pavona which is next to the Seriatipora is fine. The only thing that I changed lately was the intensity. I have two AI Primes HD and I increased them both by 8%.
Parameters:
NO3 - 2ppm
PO4 - 0 ppm
Alk. - 10 dKh
temp. - 77
Ca - 430 ppm
Mg - 1300 ppm
Thanks for any advice.

 

[Zach B]

Your phosphates being bottomed out may be causing issues