My macro just died!

[BlueAbyss]

Hmm, that's interesting, so it was only the Caulerpa... just a single species? If you have more than one species and only one was affected, I'd say most definitely a disease of some kind. I'm leaning that way anyhow, if all other things are equal and because your Chaeto is fine... try checking out the forums at http://www.marineplantedtanks.com, they may have some insight for you there.