It all started last week. My big koi started to spin out of control and died the same day. I went to the pond place and they gave me a parasite treatment bottle, with instructions to use it for 3 days. I used it for 2 days, then had to go away for 2 days. When I came back no one looked sick. I applied one more dose because I thought it had to be used for 3 days total.
The next day 2 fish died; they didn't look like anything was wrong with them. I called the pond place, and they told me not to use any more medicine until something went wrong. Today another fish died suddenly. They don't have anything on them at all. They just isolate themselves and then they die.
My question is, can I reapply the blue spectrum medicine again? And do it for 3 days again? Or is that going to harm the fish? Am I dealing with a parasite or a bacteria?
The other fish are swimming kind of fast, not like normal. The pH was fine, ammonia fine, and the change water looks clear.