Hard Corals are Dyin, Soft corals are thrivin'

[Gizmo]

As per the title, my bubble kicked off, the clam is slow to respond and my green brain is starting to die off. I've tested my Mg, Calc, Nitrate levels and they are fairly normal. Phosphates were high but I've been treating them with phosban for about a week now. On the other hand, my soft corals are doing REALLY well. No overfeeding has been happening. Nothing new has been added or removed from the tank in months. I'm at a loss. HELP!

· Calcium: ~450 ppm
· Alkalinity: ~3.89 meq/L
· Magnesium: 1300 ppm
· Iodine: 0.06 NSW
· Specific Gravity: ~1.025
· Nitrate: 5-10 ppm
· Temperature: ~80° F
· pH: 8.2