What the heck is going on, I have absolutely prestine water, no ammonia no nitrites, pH 7.5, nitrate 20, yesterday I feed the fish everything was perfect, turned the lunars on went to bed woke up and my most active most colorful emerald rainbow was dead, white and half eaten, I can't do this much longer I haven't had a fish death in a long time and now I have one rainbow dead and an Irani red that isn't eating and gasping a bit I don't get it. Mind you I just purchased these a month ago with none of them unhealthy