Zoas dying

[Wrench]

I've lost two small colonies recently and havent been able to figure out what's going on. First sign is closed polyps. Within a day or two, the may is turning brown and the stalk of the polyps begins to narrow. Eventually the mat turns a dark brown (almost black) and the polyps are dead. I've tried Iodine dips and it worked on one colony, but no others. Any idea whats going on here?

Params;

1.023
pH 8.1
Alk 7 dKH
Ca 410
Temp 80.5*

 

[adam_kips]

sounds like something that just happened to one of my small colonies that was my favorite. no idea what happened but later i found some nudi's on another couple colony's. no idea if that is what caused it to happen or not since i didn't go in for any close inspections. so maybe have a look for any pests and good luck solving your problem. if you find anything other than nudi's let me know so i can check my tank out for it.