Yellow leaves are caused by too much fertilizer or too much light. Yellow stalks are usually caused by too much fertilizer. Changing the water was the best way to handle this problem. However, the damage may have been too far gone by the time you changed the water.

You have two choices:

You can ride it out for the next few weeks and see if the plant recovers.

Or

You can start over by cutting the lucky bamboo stalk above the yellow. Find a node about an inch above the yellow part. The nodes are the raised rings that grow around the stalk. Cut the stalk and take the stock top and dip it in rooting hormone powder (local garden center carry this). Let it dry overnight; then place it in a container with a couple of inches of water. The stalk top will form roots and you will have a new plant.