Hmmm sounds fishy (no pun intended). I'm seriously thinking you got TB in your tanks. TB dosen't have certain symptoms. Many symptoms may occur, or nothing at all. Some will seem sick or some just drop dead.
Who am I? Well I am a Junior Member of the International Betta Congress and a breeder of white HMPKs, red dragon HMPKs, black/red dragon HMPKs, metallic multi HMPKs, blue masked HMPKs, and now multi color HMs. Soon to add black HMs. I will be showing in New Breeder class in fall of 2012.