sdguy - sorry to hear
i loved your anthias!
Since you've had them since november, it probably isn't aggression. Aggression kills fish much quicker then that...
I do know bartletts come in with some major flukes from christmas island. Most of the time they arent even noticeable and will kill the fish over a long period of time. The melting of the fins is pretty strange...
Good luck finding what happened. Maybe just stick with one species, bartlett or lyretails... Easier in the long run i think.