I have a happy bamboo that’s not happy
The bottom leaves are always going yellow and the water yucky
Certified GKH Gardening Expert
I see that it is in water and nothing else. It is lacking fertilizer. Growing in nothing but water will require a few drops of liquid fertilizer with each water change each week, though they can go longer between than that. Leaving stagnant water for much longer than a month will lead to infections as well.
This article will help you to care for lucky bamboo, which is, oddly enough, a dracaena and not a true bamboo: https://www.gardeningknowhow.com/houseplants/lucky-bamboo/growing-lucky-bamboo-indoor.htm