What is this white patch?

[MONTANTK]

My acro recently developed this white patch. I had a birdsnest which developed a similar patch which resulted in tissue loss. Any idea what it is? I don’t notice any pests and it doesn’t necessarily seem to be spreading.

Alk: 8.4-8.6
Ca: 420
Mg: 1320-1350
No3: 2ppm
Po4: .01ppm

 

[Perry]

Zooxanthellae concentration or lack thereof, the coral is getting more pastel as a result of low nutrients. The coral looks otherwise healthy, but a lower kh concentration and a tick upwards of nutrients will bring more saturation to the coral.
My best guess
Cheers

 

[MONTANTK]

Zooxanthellae concentration or lack thereof, the coral is getting more pastel as a result of low nutrients. The coral looks otherwise healthy, but a lower kh concentration and a tick upwards of nutrients will bring more saturation to the coral.
My best guess
Cheers

That seems to make sense. I’ll keep trying to raise nutrients since it’s easier than lowering Alk