I know this was a long while ago, but I'm sorry your fish perished.
Also I would like to say for the sake of others reading this thread; first off Easy-Life's fluid filter medium does not harm your fish. It is 100% safe, even if a child drinks it. It contains earth minerals that have not been disclosed by the producers. I was a bit sceptical about this at first however my very experienced local fish specialty store owner highly recommended it. Doing a 90% water change without knowing what is happening to your fish is incredibly foolish and is what led the fish to their demise. But I do understand you doing so.
Secondly, if the label of EL's FFM was read properly, you would have read that "After addition it makes the water turbid, because the contents become active. When more contaminants are present, this cloudiness lasts longer. In freshwater aquariums it lasts 4-16 hours (to 48-72 hours), in marine tanks 2-4 hours (to 12-24 hours) and in ponds 24-48 hours (to 5-8 days). Subsequently, the water becomes crystal clear."
This is a very good product because it is completely natural and actually fights the cause of problems in your tank rather than Prime, which creates a chemical slime coat on your fish to protect it and does not rid the tank of whatever is causing your fish to be ill in the first place.
I have never been more happy since using EL's FFM, it makes A LOT of incredible claims and from what I have witnessed in my own tank, it certainly does live up to them. And I use to always use Prime.
But just ALWAYS make sure that you research, research, research! ANYTHING that you put into your fish tanks and don't just stop at the first couple of bad comments you see. People will mainly post about bad experiences over good ones always.