[Grah the great]

No, but I'm not surprised with the behavior change. Flagfish are much more complicated than most killies in behavior...if you need proof, just watch them spawn in a shallow tank, in which males will actually protect the eggs! (Spawning them in a deep tank will result in the flagfish open-water spawning like any other member of their family, the pupfishes).

Just be careful, though...flagfish are not one of the more docile fish of their size. Some flagfish will go after their tank mates quite aggressively, so keep an eye on them.