it's been a while but hope it helps. i think i had this problem recently. my female sword and one of my white clouds got infected by this thing. they had white stuff all over their body and they became very lethargic. and it seemed that the white stuff was eating away flesh and tail regions. i quickly transferred them to a seperate tank, added cold water, and a good amount of salt. after releasing them both in the tank, the sword got rid of the white patches pretty quickly and started swimming around. white cloud was doing worse, it was actully bleeding. i changed the water daily, and the sword was fine and dandy in one day. swimming around and w/o any sign of the patch, her tail was partially eaten off though. i transfereed her back in the regular tank, and she is doing fine now, even her tail healed up. i kept the white cloud there for a few more days and it healed as well, though still has scars and is a bit shy now. you can see visible scars on it's body but she swims around regularly now and eats well.
both fish are doing okay.