A lot more information is needed regarding how long they have been acting like this, new additions, etc.
That said, the white film on the clown would indicate a brooklynella infection.
The chromis is moribund, but to save the rest of the fish, move to qt and treat with formalin.
How would they get brooklynella, I lost another chromis but never found it, I lost a Melanurus Wrasse but it did not have any visible infection of any kind, I posted those pics on here. Should I turn off skimmer? No new additions in 2 months.
Well I did add some Prime 2 days ago and I added more today. I go over to the tank and everyone is out ready to eat, with the exception of the one chromis. But gor it out before it could have died.
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With the corals looking o.k., I think you can rule out water quality issues. Off the cuff, it could be Brooklynella. Do you have a treatment tank available?
The chromis appears moribund and gramma showing skin issues and clown faded which suggests water quality issue or bacterial issue
Verify ammonia and nitrate as well as temperature not elevated
I’m not home but will get @Jay Hemdal to take a look also
Those fish have brook. The gramma and clown are covered. Everything will die unless immediate treatment is started in QT tank. Primary tank needs to fallow 76 days.