I've had about 12-13 types of Zoas over the past year and only 5 of them have survived. The ones that survive, thrive. The ones that don't survive, typically only last 1-3 weeks. There is nothing visually wrong with them ever, they just kind of shrink and shrink until they disappear. What could the issue be? I use the blue bucket of Red Sea Reef Salt and have decent lighting (for lower light requirement corals). Any thoughts are helpful.