I can already tell you, everyone is going to ask if you can get an accurate reading of your phosphates.
Also, what sort of lights are you using? What is the flow likenin your tank?
You say it is extending and closing. Is there a certain time of the day you see it close up? Most of my euphyllias are open am fully extended during the day, but once the light switches over to moonlight settings, they close for a bit before extending again. My hammers more so than my frogspawn. The only other times I ever see them close up us when something aggravates them, like a snail climbing on them, or a fish swimming by them, or me cleaning the glass right by them and stirring up the water with the movement of my scrubber.