Mysterious disease

[Ruth]

Holy Cow that is sad! I don't know about your foxface as I have never owned one but have never really heard about them being aggresive like that. I would be looking more towards water - or something that got into it. I know about a year ago I lost a couple of fish and just couldn't figure it out until I caught my son with the Raid container getting ready to spray the room. Turns out he had sprayed a couple of days before my fish died as well. I would look towards pesticides, insecticides or cleaning products somehow getting in your tank - not directly added in but staying in the air long enough to settle on the water. I know that I have heard of really bad things happening when people have used Windex or Fantastic in the same room as their tank.
I'm just throwing a couple of things out there for you to consider and don't know if it is at all related.
I hope you don't loose any more fish or anything else for that matter.