So I got 2 Banggai cardinals from dr reef a month ago and I kept them in observation for about 2 weeks just to make sure they were fine before putting them in and they were both doing fine and eating well but yesterday one stopped eating randomly and the other was eating but definitely had a decreased appetite and showed no other symptoms of anything else just didn’t eat for a day so I didn’t think much of it but when I woke up I found my cleaner shrimp eating it. All my other fish are completely fine and my parameters are also good, only thing I’ve done differently or noticed is the my nitrates are was kind of high at 20ppm and I fed them some frozen food that was sitting out for about three days. What could be the cause of it dying?