Sorry for your loss
Given your tank size, I would avoid adding another large growing fish with a yellow tang. They are quite territorial and can often fight with new additions similar to it's own size and general shape. More likely the problem with the Bfly was stress from aggression and possibly injury from fighting with the tang, damsels or both. Yellow tails are pretty good at squabbling but are usually not a threat in terms of injuring a larger fish. They can cause a good deal of stress if the new addition is already ailing.
Depending on the species of your wrasse, they do not always acclimate well to captive environments. Especially juveniles and cleaner species. The success rate with keeping cleaner wrasses alive more than a few months is less than 50%.
I would give the tank about a month to settle down before attempting a new addition. Since you have the spare 30 gal
, set it up as a QT
start cycling it now and you'll be ready for the next addition. With the damsels and tang already in residence, stick with slightly more aggressive species. Meek fish species will not fair well.