thanks jk, you mentioned temp could be the cause and i did have a heater ehiem jager stop working just before this happened. Put my hand in to check something out and the water felt cooler than usual , so checked the thermometer and it had fallen to about 75d in 1 day or less. So had a new spare and changed it right away. I set it to bring the temp up to 79d over a 2 day period , but probably the drop in temp was faster .
He didn't make it ..but I did try the epsom salts baths to no avail. I have been watching the other fish , knock on wood, nobody else has it . thanks again,