Identifying the malady is going to be the first step...is there any way you could post a pic? ics

Also, please excuse the comment, as it is not meant to be a dig at you, but don't you think there is a possibility that there are territory issues in that tank? Five fish, two of which are triggers, one potentially large tang, a goby (I'm thinking you were referring to "dragon" and not "bragon") which has the potential of reaching 15" easily and has been known to hit 24", and a blenny are most likely having problems finding their own space in a 29G tank. I'm sure you know stress lowers the resistance to illness...just a thought. ;)

W.