I just lost a discus and then the others showing slime loss clamped fins. tryed lots of water changes and other meds nothing changed, someone recommend FMG (formalin & machalite green pond treatment by nt labs) and it worked a treat, improved overnight and now eating again. This is a good alround med for Discus with mytery illnesses that increased waterchanges and worming don't cure, as it treats fungus and parasites, great for gill flukes, velvet and whitespot.
Hope you find out whats wrong and cure them, its gutting to lose such beautiful large fish
regards Angel