Desperate need of help

[Mani]

I have a 120 gallon mixed reef tank, with SPS, softies and fish. I recently started adding SPS and realized my nitrates were high. Started dosing with no pox, had a bloom of dino algae. Some one suggested Vibrant. It took care of algae but now my corals are dying. I have lost my red bubble tip that I had for over 15 years, lost all SPS, mushrooms shrivelled up, hammer coral not opening. Please advice
Selanity 1.025
Dkh 9.2
Calcium 420
Ph 8.2
No3. Zero
Po4. 0.15
Temperature 78
I am completely lost, thinking about stop dosing (12.5 ml twice a week) but afraid dino will be back.