Zoo's Closing up

[Coderad]

One of my bunches of zoos is closing up it has be doing really good since I got them but every day more of them seem to be closing up now they are almost all closed.
WHat is wrong with them?
The other zoo's seem to be doing fine and they are right beside them.
I check perameters and calcuim was a little low, but I dosed the tank so it should be back up no I will check again tonight.