What are your N03 and P04 levels at? I lost almost every single Acan in my tank. Every chalice too. The only thing that has changed, from when I had a thriving reef, was my N03 and P04 levels. I'm assuming that did it. Either way, it sucks. It's hard to keep going when things die even tho you give so much attention to the system.
Nitrates are 2ppm and phosphate is 0