Talkback: Succulent success
I don't know this particular aeonium, and can't find a reference for umbellata either. However, if this is similar in nature to other aeoniums then it is quite normal for the lower leaves of every rosette to fade, turn brown and fall. This leaves a bare length of stem below it, and gradually the rosettes of leaves sit at the end of ever lengthening stems. This does add to the character of the plant, but if they grow too long then these can be cut off and used as cuttings. Just cut off a rosette with about 7.5cm of bare stem below it, and push this into a pot of gritty compost to root. Aeoniums can survive with very little water, so do take care not to overwater!