Is this STN on Pocillapora coral?

[WGivens]

Hello All,

I purchased a Pocillapora frag 4 months ago and it has grown tremendously during that time. Over the last couple of weeks I have noticed it hasn't been doing so well and starting to lose polyps and its skin as it is turning white at the top of the coral. I have been looking online to diagnose this, and haven't been sure of the problem with all the possibilities. Would love some insight from other reefers.

In looking into my parameters, I thought it might be STN as I have been suffering with low Alk and Ph. The thing is, when I read up on STN it says it starts from the bottom of the coral and moves its way up. On my coral it is actually starting from the top of the coral and moving down. Does that matter? Here is a quick picture, would love to hear what you think is wrong and what you think I should do to heal it back to health. All other corals are looking good and healthy, this one just took a turn for the worse. Thanks in advance.

Tank size:65 gallons
Tank Age: 6 months
Salinity: 1.0255
Temp: 78.9
Cal: 450
Mag: 1340
Alk: 7
Ph:7.4
Phospate: .02
Ammonia: 0

 

[Flippers4pups]

STN can certainly start anywhere. What's your N03?

 

[WGivens]

Thanks for the reply @Flippers4pups. My NO3 is at 10ppm

Thinking it is STN, as it has slowly been eating away at the coral, and all other corals are doing well. Just didn't know if STN could start at the top, verse the base of the coral.