I changed the water and cleaned their tank today. My wife put feeder fish in after acclimating and every thing seemed ok until a few hours later. The fish that weren't eat were dead and floating at top. Male laying on bottom and we have to nudge him with the scooper net to get movement (we thought he was already dead). Female regurgitated the fish she ate and was swimming erratically for about 30 minutes, but she becoming lethargic and laying at bottom now as well. We used tap water and treated with water clarifier and cleaned tank as usual. The fish died after buying them less than 2 hours prior. Could the fish have made them sick? Nitrogen, ammonia, or some water level out of balance? Any help or advice would be greatly appreciated. Thank you!