The blue tubs I got a few weeks ago have been going strong and quite healthy until today. When I first got it, it opened within 5-10 minutes of entering my tank. And has done so for the past few weeks that I've had it. It was my healthiest and most robust specimen in the tank. Today, I came home and found it closed up. Every single head on my rock was close (there must be 20+ heads). I checked my parameters, ammonia/nitrite/nitrate are all zero. Ca and Alk are lower than I'd like but it's in the low side of the safe range. Mg is 1140, which is low! I'm working on that right now actually, I just found out it was that low and quickly started dosing to increase it back up a little. In any case, could this be the cause of them losing up today? I don't remember if they were open or close this morning when I turned on the light, was running late. My other zoas, ricordea, paly and shroom are opened up just fine. I see a few heads closed up on some of my zoa/paly, but I consider that normal since it was probably something just stepping over it. Still, the fact that my tubs are all closed kinda worries me. I did a SW iodine dip, using kent's iodine. Is it normal for a zoa colony to just randomly not want to open up for one day or should I be alarmed and take this as an early sign of something bad coming? I added a large mushroom yesterday morning. It was from another reefer's tank to my own. The shroom opened up in no time and looked healthy. My tubs showed no sign of discomfort either and are a couple inches apart from each other (this is a 29G biocube tank). Could I have added something bad into my tank that the shroom was immune to but my zoas are not? Any help would be appreciated!