Clarki's mean?


I've had two Clarki clowns for about three years now. In the tank now I have a gramma basslet, big pajama and a coral beauty. It is a 125 reef.
The clowns are mated. The female is very big and aggressive at the other clown. I understand this behavior to be normal.
I just tried to add a yellow tang and he was beat to death. As I look back on my tank since I've added the Clarks I've had some unexplained deaths.
My LFS lady (who I have faith in) thinks that it is that female Clarki and she recommended that I remove the Clarks. I 90% believe her and I was looking for some confirmation before I tear the tank apart to catch two fish. Maybe they will just swim in to my container, though