Help with deteriorating coral.

[banana2026]

this coral was fine 5 or so days ago. i haven’t changed anything in the tank other than adding a carbon infused filter pad. which i have removed at the time of these photos.
setup:
two months old
20 gallon long
popbloom light set at 30%
canister filter
purple rock
zoas gsp frilly mushrooms kenya tree and this coral(what is she?)
2 ocelaris clowns
2 hermit crabs several snails.
1 shrimp

parameters
salinity 1.026
alk 11.2
phosphate 0.21
calcium 430
nitrate 5ppm
temp 78

 

[Baldyreef]

this coral was fine 5 or so days ago. i haven’t changed anything in the tank other than adding a carbon infused filter pad. which i have removed at the time of these photos.
setup:
two months old
20 gallon long
popbloom light set at 30%
canister filter
purple rock
zoas gsp frilly mushrooms kenya tree and this coral(what is she?)
2 ocelaris clowns
2 hermit crabs several snails.
1 shrimp

parameters
salinity 1.026
alk 11.2
phosphate 0.21
calcium 430
nitrate 5ppm
temp 78

your phosphates seem to be high
any swings?
what flow is it in?
is it directly under the light or in a higher light spot?
how long have you had it?
as far as identification it is definitely a leather but hard to tell exact type due to its current state, most likely toadstool