It is suffering from too much water. Soil is very peaty - retains too much water. Drainage is most likely not sufficient since the pot is inside of a deep glass container without drainage. Stem of your plant looks like it started to rot. It may be best to cut it above the brown part; let the cutting sit on some newspaper to dry (callus). Cutting should be potted in a gritty-gravely type of medium. It needs to be in container with drainage hole (don't use any glass or similar, get a saucer). It also will need good light.

Could you please give a little more information like did you just buy it or do you already have it like for some time, how often do you water it, how much light it gets from the place you have it at or is it a self-made arrangement or bought on? From just a picture no one can really help you. Respond if you still need help because I see it was long ago you posted this.

Gabby I believe you already had a thread about these plants= here = and few ppl responded. I don't remember what soil mix you used, but Gasteria has some rot - at least leaves you are showing do. Last plant - looks like xGraptoveria 'Fred Ives' to me; but there are few very similar looking Echeverias - is one of the easiest plants to reroot. If roots were totally dry, cutting them all off shouldn't be problem. Just insert into dry mix and let it be. They root even without any soil- look at these: Plant that you think is jade is actually Portulacaria afra - not related to jade. From what you describe, it sounds like they were quite dry and now maybe some overwatering, visible on gasteria. I do not know what else to suggest except what was already said.

I think your plant is Graptosedum Bronze. I grow this plant and your’s looks normal to me. Mine grows long stems, looses leaves like this, and has the same markings on the leaves.