Corals Not Opening, Dinos and GHA

[teebucket]

My tank (29g) has been setup for about 2 months now after my tank had an alkalinity crash and I lost most of my fish and CuC. My corals had survived though, which meant I had to put corals and RFA in an immature tank. About 2 weeks ago, my RFA died as well as my xenia and Kenya tree, two corals which have a reputation for being unkillable. My zoas are not opening at all and GHA is starting to grow over some of my corals and my other corals aren't extending as much. I also have to deal with dinos and diatoms. There is also a large outbreak of Cyano that I had just siphoned out before taking the picture but it'll likely be back within a few hours.
Params (Hanna and Salifert)
NO3: 8.5
PO4 0.06
ALK 9.4
Cal 420
Ph 8.3
Salinity 1.024
Temp 81.5
Mag 1260
My RODI water also reads between 0-3 TDS.

I lost a clown and a few CuC the other day and I wasn't able to pinpoint the cause.

 

[blaxsun]

First and foremost, I'd try to deal with your algae issues. Cleaning the tank and devices in the display, scraping the glass, siphoning everything you can off the rocks and performing a large water change.

 

[teebucket]

I've been performing smaller incremental water changes over the past week or so and I've been scraping the glass and blowing cyano/diatoms/algae off of the skimmer and filter but it usually returns within hours