Green Polyp problem

[Da Reefer 25]

I have had about 12 green polyps on a piece of rock on a vertical diagnal.
They were doing really good spreading out over the rock, all of a sudden the 1's towards the sandbed were open but the ones toward the top aren't opening anymore
Does anyone know what is wrong here

Thanks

 

[cloak]

Probably nothing. They just do this from time to time. As long as your parameters are in order and your lighting is sufficient, they'll bounce back.