For what it's worth---and you have listed params---I would say ph and alkalinity matter. The one s/b 7.9 to 8.3, and alk at 8.3-9.3. It's been 10 years since I had a softie tank, but I had a good growth of the zoa species, and have it in my own head that I had notable troubles if my alk wandered: one of the first things to close would be the zoas. Of course, the fact that these colonies were in there with leathers could mean the leathers got ticked off by low alk and started spitting chemicals as they are wont to do, but I offer it as something to adjust to a better reading if you find it's 'off' in your tank.