About 4-6 months ago I had a tank crash... really frustrating. I ran out of Kalk unexpectedly and switched to an auto-dosed CA/ALK 2 part until I could re-up. I'm not sure if the 2 part was bad, or if the sudden switch was just too much for the coral but my alk dropped so fast that almost all of my SPS crashed. I had a vacation lined up so I did a 100% water change, switched back to Kalk and hoped for the best. The best did not come. Instead I got a massive algae infestation from the dying coral
Oh man!
I was just reading this whole thread like "wow this setup is sweet" and then I read this. Bummer!
I hope you pull it back together that is a sweet looking tank!