I would do as Daisy suggested, repot to smaller container. Will give you a chance to check condition of roots too. Add more pumice to your media to make it well draining. With some succulents, they will naturally drop lower and older leaves, as what your plant is doing. I would not panic much as long as I see the tip end is continuing on growing new leaves/rosettes to replace it. What will make me worry is if the base of the stem looks mushy and rotten, it will mean your plant is getting overwatered. Then you will have to cut off the rotten part, allow it to callus and heal.
Part shade with good light will be ideal till it roots again properly, if in case you have to cut it down and replant.
