I have three Rods Onyx clowns in the tank. When I bought them as juvies, I have over a dozen RBTA in the tank. Let just say that after about 6 months the RBTAs were replaced by different anemones....
Two are in a gigantea now and the other one is in a frogspawn. The fading of A.Percula colors in BTA is real. It might not happen to you but it does happen.
If you search back on other posts, you'll see that this issue has been brought up many times.
Also, Magnifica(or Ritteri) can cause A.Perc to fade as well.