Yama,
was that yellowfin just placed in the tank? It seems like that was the case becuase fairy wrasses rarely fight if they have been living together in a tank for a long time. If he is a new inhabitant for your tank then the likeyhood is that you didn't give him and the rest of the tank enough time to get used to each other. Using the specimen cup method would likely eliminate that problem because the lubbock's would have grown used to the yellowfin and the yellowfin would have had some time to build up some moxie to stand up to any bully that wanted to keep his territory.
If you just scroll backwards on this thread a bit you will find all the info you need to use the specimen cup method. Since you've already pulled the Lubbocks out I suggest that you keep him in a separate hospital tank for two weeks. Have him forget the territory he had in the original tank. After two weeks place him back in the main tank using the specimen cup method. This should work for you.
Let me just say this for everyone that has questions about what fairy wrasses are compatible with other fairy wrasses.
Just about all fairy wrasses are compatible with all fairy wrasses.
You really need not worry about species vs. species or breed vs. breed.
What you need to worry about is the following:
* Never place two supermales of the same breed and size in the same tank
* Never overcrowd your tank with fairy wrasses. If your tank is overcrowded the wrasses will fight....not because of breed....but because of territory.
* Placing similarly colored fairy wrasses together is not implossible but it should be avoided by newbies. Examples: avoid placing pink margins with lineatus/ pyle's with rhomboids
* When placing similarly colored species together stagger the sizes and ages of the fish.
* Keep your wrasses well fed. Fairy wrasses need to eat well or that can make them cranky as it relates to territory.
* Be more concerned about compatibility with completely different breeds of fish or animals that do attack fairy wrasses such as: Some Anthias, Dottybacks, other wrasses like Sixlines, carpet anenomes or tube anenomes (notorious wrasse catchers)
Again, it's not so much a question of fairy wrasse breed or species but rather a question of how YOU the hobbyist introduce them into the aquarium.