As far as I know, these brains don't split like mushrooms do, they just keep adding on (for lack of a better term).
I have a Trachyphyllia (you probably do too, wellsophyllia is an old designation no longer used, and I believe even T. radiata is being dropped, they're lumping them all into Trach. geoffry (sp?))that has multiple mouths as well that I've had around 2 years I guess and there's no sign of splitting.