I've had my two bamboo plants for about 6 years now and they've grown to 15". I've kept them in a tall glass vase filled halfway w/water (so about 1/3+ of the stalk is immersed in water). About a year ago, I added some glass stones to keep them propped up. I usually just water them about once or twice a month, which means adding filtered water when I see the water level has gone down about an inch. Have had a few yellowing, browning/drying leaves, but otherwise they seem fine. Today, I discovered one of the plant's stalks has turned completely yellow though remains firm. It's shoot still has nice green leaves. I just washed out the vase, removed the stones and replaced the green stalk back into the original vase. I've placed the yellowed stalk into a separate, washed vase. Is there any way to save this yellowed stalk? Or cut off the green shoot and root it? I don't see any evidence of spider mites or fungus (like I've read in prior posts). I know I should use distilled water (and did that awhile back when I first saw that the leaves were yellowing, but didn't see a change.) Thank you in advance.