Zoa's are pretty resilient but not indestructible. I would be concerned with why they're not opening, and I don't think it has anything to do with your parameters. Some Zoa's are light lovers, others are dark dwellers, and it's difficult to know which ones are which without playing with placement. The last time I had Zoa's close up on me (the colony was sharing the same rock with another colony that was open and flourishing) it turned out to be light intensity. They started opening up when I turned the lights way down, and when I say way down I mean Max intensity on the light was 40% and I turned on acclimation mode to reduce that value by 70%, so I guess they were around 12% or so total light output? I would look there, personally. It's also worth mapping the PAR in your tank... Rent a PAR meter either online or at an LFS, or if you know there are people around you who will pay you to PAR map their tanks, just buy one if you can turn a profit.