Cardinals suddenly looking sick

[Slocke]

I bought 4 Banggai cardinals about 2 weeks ago. One never took to the tank and wouldn’t eat anything eventually dying in isolation. However the other 3 looked really healthy used to eat really well and were super bright in color. However last night only one came out to eat and that continued this morning. The other two hide in caves and look diminished. They looked perfectly healthy 24 hours ago and the only thing that’s changed is I added a new powerhead yesterday right before they started acting odd.

It’s a 110 gallon they share with a couple clowns and a clean up crew. All fish are captive bred. I feed them 1 cube of frozen carnivore blend a day.
Chemistry
77F
1.0245
Ammonia 0 nitrite 0 nitrate very low
Alkalinity 9
Ph 8

ive also been dosing eight four for a few days

 

[blaxsun]

It might help if you can upload a few images.

 

[Slocke]

So I turned off the new powerhead, removed 25% of water to do a water change after a few hours they came out and seemed more normal. At least 2/3 are eating now. Can increased flow stress out fish?

It’s a second Aquamai KPS which would have added about 1000gph to my already 1500gph system. So about 15 increased to 25 turnover per hour

 

[Slocke]

Sorry if I’m overreacting
They’re usually very active at night and to see them hiding in corners all night was scary.
and I’m only a month into this hobby

 

[Sharkbait19]

Any aggression from the one that is still out?

 

[Slocke]

That is the biggest one and I think it’s paired off with another one as they are usually together and apart from the third. Haven’t seen them bully the third but certainly possible and that’s the one I’m not sure is eating.

 

[blaxsun]

It’s a second Aquamai KPS which would have added about 1000gph to my already 1500gph system. So about 15 increased to 25 turnover per hour

Just a clarification, as it's in-tank this isn't turnover - it's just supplemental flow. As the fish are still relatively new, it's hard to speculate. If most are eating that's a good sign.

 

[Slocke]

Yep
It’s all looking good at the moment. May move and turn down my powerhead though as I do think it bothers them. They don’t seem to be strong swimmers.
Thanks for being supportive of my overreaction.