I need some experts & experience help :(

[Reef_dachs]

I am dealing with something in my tank that I can’t identify. It looks similar to GHA but is white. It flows similar to GHA & comes off objects easily with a toothbrush.
It is invading my tank and is killing my corals. It appears to creep up the base of the skeleton and maybe suffocate the polyp head.
It’s killing corals I’ve had for years and very hardy corals like my Duncan & Trumpets.
I originally thought it was some type of sponge when it was only in the rock work but as it’s grown I’m thinking maybe it’s some type of bacterial infection or growth?

I am currently doing (2) 10% water changes as that seems to help for a few days.
Current parameters are below and they typically stay in this range on my weekly tests.

Alk - 8.7
Mag - 1350
Ca - 430
Salinity- 1.026
Temp 77
P04 - .16
N03 - 8.4

In the pics you can see the growth I’m referring to and where it has started to kill the coral bases. All the corals appear to die from the rim of the head first.

The tank is mixed reef, 130 gallons & 4 years old.

 

[Reef_dachs]

You can see the white film better in this pic

 

[ryanjohn1]

I can’t see it in the pictures.

 

[ryanjohn1]

You can see the white film better in this pic

Can u circle it. It’s tough to make out

 

[Reef_dachs]

Can u circle it. It’s tough to make out

I did. Thanks!

 

[JGT]

Not seeing anything out of the ordinary or particularly onerous. What’s the issue?

 

[ryanjohn1]

I did. Thanks!

Could the corals have been receded already and algae is just taking advantage of the open spaces?

 

[ryanjohn1]

Did you have any swings in parameters recently?

 

[Reef_dachs]

Could the corals have been receded already and algae is just taking advantage of the open spaces?

No, this literally happens quickly.
Once I notice the coral isn’t opening fully it takes about 2 days for it to die off.

 

[Reef_dachs]

Did you have any swings in parameters recently?

Not that I know of. I test weekly before my water change and they’ve been quite consistent.