Tip cuttings can be rooted. If the yellow leaves are on the inside or lower parts of the plant, it is probably because the plant has been kept too wet. If they yellow suddenly and then fall, it usually indicates a sudden chill. If the plant isn't getting enough food, the newest leaves will develop a lighter, almost yellow color. When soil pH gets too high or low, it keeps the plant from being able to use the available food.
Several factors contribute to lanky growth.
Most likely, it is too warm. It can also be an indicator of too little light. Plants often loose their variegation when they are grown with too little light. The root mass may have dried out. Submerge the pot in a container of water until the air stops bubbling to the surface, then allow it to drain.