Euphyllia: Not thriving/ one loss

[RxReefer]

Hello all,

First time poster, but lurker for nearly a year. I returned from two weeks out of the country on vacation and have some very unhappy corals. My hammer appears to have unfortunately passed away. My frogspawn is retracted and appears to have tissue loss.

Tank setup and cycled 9/2021; no issues noted prior to travel and parameters had been stable.

Parameters:
Temp: 79 F
Salinity: 1.025
Calcium: 495
Magnesium: 1275
NH4: 0
NO2: 0
NO3: 0
PO4: 0.27
pH: 8.2
Alkinity: 9.1

Tank/Setup
IM Nuvo 10
Filter floss
Carbon
GFO

Tankmates:
Clowns x2
Caulastrea spp. (Metallic candy cane)
Discosoma (Orange Discosoma Mushroom)
Sinularia dura (Green cabbage leather)
Zoanthus (Orange rainbow zoa)
Euphyllia divisa (Blue tip frogspawn)
Euphyllia ancora (Gold hammer)

Frogspawn:

Hammer:

Tips/ advice appreciated in advance.

 

[T-J]

No nitrates. High phosphates. Looks like diatoms in the pics. Don't see any coralline growing.