1 Head- Half Dead Half Alive??!??

[Mothertucker]

My torch coral has been doing very well the past 4-5 months I have had it. I did a 20% water change and half of the head shriveled up. My levels are good, my pH keeps fluctuating, but I am working on keeping it steady. The coral has only one head, so I don't think I can frag it and keep one half....

Thanks for any help in advice