zoo's not opening

[catfishcity]

i have a lot of zoo's in my tank and i have noticed that most of them are only opening about 1/2 way. some open all the way and some dont. what is going on?

 

[jackri]

What's your water parameters and lighting situation?

 

[catfishcity]

my params are fine.
ammonia 0
nitrite 0
nitrate 0
ph 8.2
phosphate 0
i have a 72w over 24g nanocube.