Are my Mangroves dying?

[Seriak]

I purchased 5 mangrove pods about a month or so ago and have noticed that most of them are slowly turning brown. There is usually a small brown patch at the bottom and it slowly works its way up until the entire pod is brown. It is still firm and not squishy, but I don't know whether I am supposed to assume that it is dead or not. Two of them are finally sprouting leaves out the top and one just breached the water line. But the other three are all going brown.

Oh and I have quite a lot of Caulerpa in the tank as well. I know that a piece of my caulerpa rooted into the bottom of one of my pods and the whole thing turned brown and went squishy like it was dead. I ripped the caulerpa off of it and it firmed up but it is still all brown.

Chris