dying tank

Salinity: 1.025 No3: 10 Po4: 0 (I guess that’s why?) PH: 8.4 Calcium: 440 Magnesium: 1050 Alk: 10.0 what the heck!!! Guys what is this algae? What are those white tubes growing under my rocks?? I’m so sad everything even my zoas are dying like what the heck

If you go to this (https://www.reef2reef.com/threads/candy-cane-coral-splitting-or-dying.962664/) you can see where the problem started, then I made it worse. My candy cane started off dying the Par was way to high. I moved it to a shaded area but for some reason one night I added calcium to my...