I have a Yucca Cane plant that has been in my office for about a year and a half. It is fairly healthy - in the same pot as purchased, right next to a big window for light, and I don't believe I am over watering. Some of the leaves are turning brown. One cane is almost all brown/dead leaves. How do I get the dead leaves off? Trim them? And what could I do to possibly avoid future dead leaves?