Hi guys,just joined.I had a gourami with a bent spine,read that its probably TB.Unfortunately I do not have a quarintine tank,so the fish was euthanized.Very upset about that but I didn't see any other options.My question is what else could it be? If anything.It just showed up in the last week.The tank is a 96 gallon corner bow with 20 fish.Its filtered with 2 Hydor 600 canisters.Ammonia 0,PH 6.8,Nitrate approx 35 ppm,nitrite 0.Both GH and KH are approx 50-100 ppm.The other fish in the tank show no signs of disease and have good appetites.Should I do anything at this point? I'm quite nervous many of these fish I've had for guite some time.My Koi angels are 7 years old.Thanks ahead of time for any info or suggestions