Now that the emergency is over, it is time for some reflection to avoid future issues like this one.
First, you (silencedogood) must understand that every substance added to the water in the aquarium will get inside the fish. Fish continually take in water via osmosis through every cell, and via the gills. Anything in the water gets inside the fish, in the bloodstream and internal organs. This is detrimental, always. The only time it is beneficial is when it is essential for the health of the fish--specific medications/treatments for very specific issues.
Any additive that will or even may kill something does not belong in a fish tank [except for the afore-mentioned disease treatment issue].
At the first sign of fish distress, do a major water change using only a good conditioner. Colin explained this, as have others. There is nothing beyond a large water change that will benefit in such situations, and it is the only way to even consider saving the fish.
Colin also correctly mentioned that the damage this has likely done is permanent. Even if the fish survive, they are no longer as strong as they were, and this can lead to other problems down the road. And always a shorter-than-normal lifespan as a result.
We all learned this and most the hard way. But now we know.
