Help me save my koi from unknown parasite

[Britbrew]

In desperate need of help/advice. I HAD 3 healthy adult koi (5/6 years old) and out of the blue on Tuesday 9/17 I found one of them stuck in between a tortoise statue and the rock wall. The pond set up has been the same for 2 years they have never got stuck ANYWHERE. I got her out but she was swimming sideways/upside down. I then gave her a 15 min salt bath in separate container when I placed her back in she looked normal. The next day, another fish was found belly up with his mouth open so I immediately jumped in the pond got him into a salt bath but after 2 rounds of parasite treatment on the pond…he is still not recovered. Last night I found my butterfly koi stuck under the water fall. Placed her in salt bath but a few hours later she was dead PLEASE HELP ME BEFORE ALL OF MY FISH DIE

 

[Lisak1]

Have you tested your water?

It does sound like they are wedging themselves in places where they will not float away. When fish are sick or dying, they lose the ability to swim, and they may just be trying to stabilize themselves by finding a place where they can rest.

 

[Stephen Noble]

Do the fish have any signs of illness (other than behavior) such as spots, fungus, red lines etc?
Agree with @Lisak1, test the water. How large is your pond?

 

[j.w]

@Britbrew
I too was wondering how big your pond is and what are the water test results?

 

[WaterGardener]

What parasite treatment did you use? I also would like to see your water tests results. Those could be a big help.