The article linked in my response does not specifically call out clowns as the death magnets, because Brook infects all fish.
Some fish have a higher tolerance and there is even evidence suggesting tolerant fish will build a level of immunity after repeat exposures.
Unfortunately, there is no way around the following path(s):
1. Don't add any more clowns to your tanks, they are sensitive to Brook and Amyloo.
2. If your fish do not seem to be stressed or affected in any way, are eating well, are not discolored, are not breathing heavy: Leave them alone.
3. If you fish are breathing heavy, showing a white slimy coat on the dorsal area, follow the treatment procedures in the linked article.
Regardless of the current situation: don't buy any clowns for 6+ weeks and when you do; buy some that have been conditioned(well fed and acclimated to captivity). It is unfortunate, but many of the smaller clowns available to us arrive malnourished and very susceptible to disease.
fwiw Reef Central has a Disease Treatment Forum as well and "Brook" has a sticky thread of it's own:
http://reefcentral.com/forums/forumdisplay.php?s=&forumid=87