I havent cheated but 3 of the pokemon in my party turned into bad eggs after a normal battle with a trainer. Does anyone know why this may be? Haven't used action replay and had one global trade over the net.

I havent cheated but 3 of the pokemon in my party turned into bad eggs after a normal battle with a trainer. Does anyone know why this may be? Haven't used action replay and had one global trade over the net.