Percula not eating and staying at the same place with a open mouth

[SethIstanbul]

Hello Friends,

One of my percula is not eating , staying at the same place with a mouth open. What would be the cause? I have 2 percula and a small blue tang with a 120 lt tank. with some corals.
All the water parameters are ok. All other fishes are ok.

Thank you for your helps,

 

[fishguy242]

#fishmedic