I have a tanganykin set up , lamps, calvs,frontosas,julis,tropheus,and syd cats. i had a topheus duboisi pass. it was 1yr old, a baby when i purchased it, ph , hardness,ammonia,nitrate,nitrite,clorine all ok. no sighns of ich no tank bullys. one day ok dead the next. although his yellow stripe was faded which was unusual. possably stress about being sick ? does anyone know what happened to my fish