just checking cause i know he has a little bit of the white type up in the back of his tank.
the only thing that i have seen happen to xenia is that when it doesnt have enough light it goes very thin and tall and looses its feathery look on the polyps, (hasnt happend in my tank, i gave a frag to someone that didnt have enough light but then they upgraded soon after and its starting to come right now)
as for the colour change i don t know (not that i ever do )