I have a small white amenone with purple tips, not sure what type it is, I'm pretty new at all of this. I have had it about a month, and it has placed itself down on the sand in the rocks. I doesn't get much light but seemed to be fine. But tonight looking in the tank it has closed all up and looks like a big marshmallow. Have I killed it? What causes them to die, I have tested my water and everything is in order, the salt is right on and the temp is fine, any suggestions??