Duncan coral not opening

[darmac]

Hi all,I bought a four head Duncan roughly two months ago,since then it went from 4-12 heads and two days ago never opened and hasn't since. Does anyone have any idea what could be causing this. All params are spot on.

Darren

[mrgk]

Dose any iodine into the tank?

[darmac]

No just mag,alk and cal,all other corals are doing great and growing

[mrgk]

Tried target feeding it?

[darmac]

All corals get target fed once a week,its strange that its the only coral not opening up,would a coral dip help,maybe something irritating it?