One of the big problems with fish disease is getting the correct diagnosis. This is often complicated by the fish having more than one disease at the same time. once a fish is weakened they are much more prone to getting other diseases. In this case, the white patch may have been some type fungus but then the mouth not closing sounds like an internal parasite or some other problem. I would not use any medicine at this time. Until other fish show signs of problems, I look at medicines as potential to cure or potential to upset the whole tank system it the meds kill the good bacteria. I would advise some study on various signs to look for and form a plan but do nothing now.
Also any extra attention to keeping the water super good is always a good idea during times of stress like this.
Last edited by PlantedRich; 06-04-2014 at 07:23 PM.