I'm sorry to hear that.
It sounds like your tank has not cycled properly since restarting it, and adding all the fish just increased the toxic levels. The test strips that your LFS
is using are really worthless, IMO
. You need the liquid test kits. I'm guessing you might have high ammonia, nitrites, or low pH. You're gonna have to do some serious water changes lol. Also, just my practice, but whenever I add new fish to a tank, I also add some Stability. It's basically bacteria in a bottle. I have good luck with it and have not heard anything negative about it. You could try it, but definitely need to do water changes. Best of luck for your fish