Yellow Tang went from happy to dead in 2 days

[AJ]

So, I have no idea what happened.  Our yellow tang was happily swimming and eating Saturday, then by Monday night, she was dead...  All other fish, livestock and corals are doing great.  We did a 20 gallon water change (25%) to be safe, but I'm still baffled by this occurrence.  Any ideas what may have happened.  BTW we do not have ich, all fish and livestock go through a rigorous Quarantine phase before entering the DT.

[Twizted1]

How long have you had the tang in the dt? Any signs of fin tears, miscolorations, anything like that?

[AJ]

The tang was in the DT for 2 or 3 months.  I did not notice any fin tears or anything of the sort, only a discoloration in her head as she was passing away.

[Twizted1]

It's really hard to tell. Sometimes there's something wrong with them that takes time to show. It could have been caught with a chemical of which name eludes me currently. Sometimes it's hard to figure out.

[Wall_Tank]

Sad when it happens, but sometimes they just die.

[Viggen]

Yea at times there is no explanation

My xl orange shoulder who was extremely fat and ruled the tank died two days after a water change.  The day after his head was buried in the rocks breathing hard and the second day he was dead.  Totally healthy, 9plus inches long and over a half in thick.  No other fish has been sick