Sorry for your losses
You were posting about setting up a new tank
just a couple of days ago so I hope you didn't add all these fish to a new tank without first doing a fishless cycle
. If so improper water parameters were most likely the death of your fish and not the Yellow tail.
My yellow tail is very tame but active. Also Dragon Wrasse
are not the hardiest of fishes from what I've read and been told by other aquarist.
How are your water parameters currently?
For removing problem fish read Get Out of My Tank! Fish Removal Tips & Tricks
by Steven Pro.