Oh! I am soo very sorry!
Fish Herpes? (I am not as up on many diseases..there are soo many more now)
It wouldnt respond to a common treatment I bet.
had fish looking like they were wearing angora sweaters (thready hairy mold like scum spots) at one point of the week,
It a month back, I almost got wild Rams?Loaches and wild rams all in one tank. The loaches were milling around at speed when not bunched in one corner, and looked like the worst case of ick Plus!
He said it was fish herpes.
He was expecting regression of syptoms by the week's end..
Only like 6 in loaches made it. I am glad I didn't let Anna buy a pair.
Though Melafix symptoms sound like that too...sudden surface gasping followed by death with gills flared open.
Melafix only does in a percentage of labyrinths (which is why betafix was formulated, not that it isn't mistrusted by some).
She just lost so many betta to a tough bout of sudden diseases nearly beat that got latched with a tough bacterial. And they didn't all share tanks only the room wall.(see caring vet thread and to the vet we go thread). With fish it is just so easy to miss that one important symptom that IDs the cause.... they are not as up in your face or similar enough in basics to guess like pet mammals..
Poor finny friends!
It does sound like your disease carrier, the new fish, had muti-infectives like our poor fish