Orange false perculas vs black perculas

[Bigshow]

I may have a problem. I have had a pair of false perculas for about 7 weeks and now i have purchased a black percula. I have read that this wouldnt be a problem but the false percs seem to be ganging up on the black perc. Any ideas or comments?

[Bigshow]

The black perc just keeps swimming around the whole outer edge of the aquarium.

[VacavilleFC3S]

anytime you have 3 clown fish in 1 tank, 2 will pair off and pick on the 3rd till it is dead