Plate Coral / Heliofungia

[Pisces3473]

I know this guy is in trouble, I'm just not sure what to do about it. I left my office last Friday and had noticed the fish were all just kinda hiding out that day. I figured no big deal, just like corals fish do different things on different days. Then when I came in on Monday 3 of 4 fish were dead and this coral is in serious trouble. I tested the water and the big three were off the charts. I added an entire bottle of Bio-Spira and 24 hours later the Ammonia, trites, and trates, are back in line. I'll be testing more again later, but in the mean time anybody got some advice on what to do with this guy?

Thanks in advance!