open brain colour/ zoo?

[outtafocus]

I have a red open brain coral, which up until the other day was always a nice deep constant red.
The other day, a portion of it became an almost flourescent pink. It is still eating as before and has lost no visible size.
The following pic makes the coral look sickly, but the real thing looks better.
What do you feel could cause a minor colour variation?
I have changed nothing during this time, except the standard 10% bi-weekly water change, and no lighting changes either.

Once possible thing could be from a nearby coral, I believe this coral is a galaxia. It may be close enough to reach out and touch the brain, but I have never witnessed it do this, I have seen it reach out though.
These two corals have been neighbors for 4months. The "galaxia" is visible just behind the brain.


Also, all of the zoo colonies I have dont seem to grow, they open fully most of the time and seem in good health, just never increase in size.
I had one small frag of green zoos (10 polyps) which just seemed to slowly disapear to nothing. I checked all frags for and nudi's or snails and no sign. Any tips to make them pop?