I haven't had that problem. In fact, mine was kind of crazy... I bought the fish, and as soon as I got home, we had an emergency and had to leave right away, so I just let it go in the tank w/o acclimating... The fish is still alive and well after 2 months... getting fat too.. (BTW
don't try this with your fish) I would suspect the Flame Angel or the Fairy Wrasse could have had something to do with it... I think the 6 line is a very hardy fish... I would try acclimating slow drip method, for at least an hour, maybe two, and then add it to the tank...It sounds more like aggression to me though...
What are the water params? If you post all of them, we can possibly help better..