Brooke and MV look similar and Brooke does not respond to copper to well so fish die and people assume they started to treat for MV to late. You should confirm MV is cause of death because these two diseases are totally different and react different Brooke can kill in 24hrs from the time you see it on the fish. Brooke is way more common and though it is a clown fish disease it will move on to many other species of fish in search of a host.

Bill