Corals acting Strange!!! any ideas?

I thought my corals were being a bit fussy the last few days but now im beginning to become concerned. I have a Zoa that was open and now its closing, I moved it because hermits were bumping it and making it close. its slightly opening now. my GSP is completely closed but was happy just a few days ago. my hammer coral is THRIVING and very happy however. I do have what seems to be a diatom bloom happening again but my water is showing no ammonia and no nitrates. I use RO DI water from my LFS who only deals in saltwater life and has a great reputation. just tested it 5 minutes ago! wondering what could be the issue? pics to follow.