Mysterious deaths. Need help

[cane]

My current tank has been up for a few years (Upgraded from another 2 yr old tank I had). Everything has been growing great. It's a Mixed reef so I have pretty much every type of coral. But recently I have been loosing some of my acans, trumpet corals and I think one expensive mushroom unless that thing floated off somewhere else in the tank as I have seen before. Colors are the best they have ever been for everything else. Even some pieces that didn't have the greatest color in the past look great. Help me find the problem please.

Recent changes:
Switched from Radion light schedule to similar Apex Schedule
Switched from ESV to Tropic Marin Parts A/B/C (Stopped C after 2 weeks in case that was the problem)


Tank: 8' 350gal system running an Apex controller
Sump: Basement with skimmer and Chaeto, carbon
Lighting: Gen 4 Radions ran off Apex Schedule
Flow: Medium to High
Dosing: Tropic Marin A/B, Amino
Running Carbon
Run GFO occasionally

Temp: 78
Ph: 7.88
Alk: 8.5
Calc: 430
Mag: 1350
Phos .07 (try to keep it under .05)
Nitrate: 0

I think that is everything

 

[Eleni18]

Parameters?

 

[Uncle99]

What’s salinity, and how stable do you keep it, that’s the foundation for everything else.
Nitrate should not be zero, 2-10ppm is a good area.

 

[cane]

Parameters?

All posted above

 

[cane]

What’s salinity, and how stable do you keep it, that’s the foundation for everything else.
Nitrate should not be zero, 2-10ppm is a good area.

Salinity is 1.26 and the tanks pretty stable. But these corals have made it through my mistakes in the past with no problem which also makes this even more mysterious. I’ve never been able to have those nitrate numbers but the tank has always still done well and grown everything with ease.

last three pics show some of the corals that are dying. The others are just some random pics of the tank.