I recently purchased a small lucky bamboo (4 stalks, about a foot tall), and it seemed fine in my home for a few days but then I noticed some yellowing of some leaves and the stalks (from the top down). The yellowing on the leaves starts from the tip and moves inward. It is planted in soil, not water. I have only watered it when the top 1 inch of soil is dry and have used no fertilizers. It is in a basement room with a south-facing window, but since it is the basement, the light is obscured by the window well, so there is not much in the way of direct light. I inspected the roots and they appear healthy (kind of a beigey color but not mushy). The yellow part of the stalks are still firm. I try to use only filtered water (I just use a Brita water pitcher - not sure that does any good), and I also have a pH balancing kit, just in case a certain pH level would help the plant. Any ideas what could be going wrong??