Stn from the base or bites?

[Luisreefmexico]

Hello
I recently detected some acroporas with blenching from the base
Colud you identify if it are stn or maybe someone is eating my corals?
alk:7.3
Mg: 1250
Ca:500
pO4: .17

 

[P-Dub]

Hello
I recently detected some acroporas with blenching from the base
Colud you identify if it are stn or maybe someone is eating my corals?
alk:7.3
Mg: 1250
Ca:500
pO4: .17

Looks to be a highly shaded area on the last two photos so that is the likely culprit. In the first two photos I can't say that I see an issue. Could be STN...