Corals Not Opening as Much

[nondan]

Hey Guys,

I have kept fish only tanks well for the past few years, I have recently set up my new Aqua One Reef 400 and has been doing really well. (Running for 7 weeks, fish in for 3 weeks, coral in for 2 weeks)

I have a Seneye Reef telling me my Ph: 8.22 - 8.30, Ammonia very low, from 0 - 0.006 and temperature is also good.

Recent calcium test was also good, around 400ppm, 0 Nitrite, and iodide test also good.

My problem of late has been that 1 of my 2 Hammer corals has been more closed than opened, and also my cataphilia has not quite been spending as much time fully expanded. I also have a daisy doing the same.

As my coral knowledge is very low, Im not sure whether they are getting enough nutrient or whether its something else.

I feed them 2 serves per week of "Reef Snow", and also a weekly dose of Strontium supplement.

I have only had the corals for 2 weeks but would like to learn to understand them better.

Any ideas what the cause could be for this behaviour?