One of my ADFs has died. No idea what from. Fed it yesterday and made sure it ate (by distracting the betta with a mirror) and it seemed ok. Today it was sat in its favourite place on top of the filter completely lifeless. No sign of physical damage (there has been no sign of violence in the tank at all) and the water quality is fine. A mystery. All eyes are on the remaining ADF. Thats when I can see it, its much smaller than the dead one. Fingers crossed.