Aeoniums are so-called 'winter growers', but really should be called 'summer dormant'. Seems odd not to water much during the hottest time of year, but the plants will thank you for it. You have a bad case of stem rot, certainly caused by watering when the plant was dormant, and from poor soil conditions. But there is good news, the fall growing season is underway, and it's a great time to take cuttings. In your case, there is no time to lose.
The fungus is very advanced, having traveled up the now collapsed main stem, and into the branches. The only solution is to cut those little rosettes free, and re-root. Here's what to do:
Cut the rosettes leaving less than an inch of stem. The cuts must be ABOVE the level of rot, or the cutting will fail. You can see the fungus in the dark colored areas close to the branching points from the main stem. You will need to cut close to the rosettes, examining the cross-section of the stems for any dark vascular tissue. If it is there, keep cutting towards the rosette in 1/4-inch increments until the cross section is clear. It's OK if there is no stem left at all ;)
The cut ends must dry in the air for about three days to callous over, then plant in dry soil that is about 75% inorganic materials like gravel, perlite, pumice, etc. No sand! No peat! You can mist the plants every few days. Keep in bright shade, no direct sun during this time. Use very small pots and very quick draining soil during the re-rooting phase. Do not water thoroughly until the rosettes have started new growth, or you will rot the cuttings.
Some of those rosettes may be to far gone to save, but you are fortunate to have many babies. You should be able to save several, leaving you with more plants that you started with. :)
Take action now!
Brad
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Recreate the same bed on the side
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