Xenia is supposed to be so hardy and I had about 5 good stalks of it and now I'm down to 2. All of a sudden, the stalks just shriveled up and it looks like the heads have fallen off of them and they died. They were fine for so long. What could make them do this all of the sudden? All water parameters are excellent - tested the other day and everything was at zero. I don't remember the figures for my calcium and alkalinity but it was definitely in normal range when tested. The tank is a 120 tall with plenty of water flow, brand new power compacts and actinics.