I don't know if your situation is the same as mine or not, but I ran into something similar with my E. 'Chroma'. Since then it hasn't happened to any other plants. I hadn't used any fertilizer. I'm sorry to hear of your situation. I really hope people can help.

[https://www.houzz.com/discussions/what-in-the-world-is-this-black-stuff-on-my-echeveria-dsvw-vd~5140146[(https://www.houzz.com/discussions/what-in-the-world-is-this-black-stuff-on-my-echeveria-dsvw-vd~5140146)

It looks likes yours has some extra features that mine didn't have.

Hi Jeff, thanks for the reply! Yours does look like standard stem/root rot, which I do have experience with in some other plants, though feel certain this issue is not the same, as none of the plants have shown any of the symptoms typical of this type of rot, like lack of structural integrity, wet/gooey-ness, or odor.

Very interesting to read that many people have had such issues with E. 'Chroma', however.

Not that I would know how to diagnose, but if you've cut off the stem of one of them, did you see any black inside? Mine had some right in the middle. Also a black dot on the dropped leaves where they were separated.

Edit: just missed your comment. I thought you probably had seen my post, and I could see yours has more issues. Sorry mine couldn't help more. I wonder what's wrong with those Chromas.

I have never had this happen until about a month ago I spotted this really pretty white/pink little Echeveria. Looked worse for wear, but I thought I could give it a little tlc and it would snap back. Slowly it has dropped its leaves one by one. It has the same issue little black spots on the leaf. It’s only pretty much where the leaf and stem meet. So the leaf ends up falling off.

Hi Kara, yours do look somewhat similar, though the bottom leaf looks truly like rot, which mine tend not to. The dark patch is not mushy at all on mine, and mine do not look like the patch "eats" the inside, but rather spreads along the outside.

Additionally, my plants are all indoors and are all bottom watered. I take great care to ensure no water gets in/on the leafs so that I don't get crown rot (being indoors, I know how the lack of airflow can help that kind of rot along). I am skeptical that is an overall airflow issue, as this issue only started around the time I brought home that E. 'Chroma'. Some other things happened around this time too (transition to gritty mix, introduction of Miracle Gro), but I still went quite some time before that without this issue.

Hi laticauda.. Wee bit thrown here, my local extension office of what? I'm not opposed to testing (and mighty curious), but I'm not sure what office you mean.

I used this service once. It's a county--as in counties in states in the US--extension (I don't know what an extension is) which provides help with horticultural stuff. Like this in Milwaukee county:

https://milwaukee.uwex.edu/horticulture-programs-and-services-of-milwaukee-county-uw-extension/gardening-questions-answered/horticulture-help-line/

But you can also take plants or samples in for them to look at. I lost most of my African Violet collection once. I brought a plant in and the horticulturist said it was crown rot. I found that hard to believe, but at least got a good opinion on it. I suppose the help you get can depends on the person you see and the tools they have to diagnose. It would be nice if they could do some sort of biopsy and tell you what the condition is and exactly how to fix it.

Oh my goodness, what an obtuse name for an institution. I've heard "Extension office" all my life and thought it was referring to something like a branch of another institution. Thank you! Had no idea this was an option.

Your county extension is a satellite office of the State Dept. of Agriculture. Most folks just call it the county extension. They can help in many ways, such as helping you find a bee keeper to come get a swarm. They can also test your soil for fungus (ganoderma is a biggie killing palm trees here) and other contaminants. They will identify pests and recommend treatment.

Our county extension sets up in a local park on 2 Thursdays a month. They also have a booth at nearly every plant show/sale/swap.

Ironic side note - the Florida Dept. of Ag. also handles applications for a concealed weapon license, but not at the extension office. They have a special office for that, and hunting permits. I don't get the connection, but there it is!

Thanks, all! I've sent an email through their website and will give them a call if I don't get a response.

I say call it a fungus and treat those plants! I think it looks and smells like a fungus, its a fungus.

If you call, ask to speak with a master gardener. If they are not satisfactory in their replies, call back another day. My understanding master (lol @ my phone changed this to 'disaster') gardeners are volunteers from the public that go through a course. If I'm incorrect, please someone correct me.

Ask if they have a lab (every state should have one) and if you can get the plant rot cultured to see exactly what it is. There are different types of fungus as well as different pathogens that cause rot. No use treating it for something it doesn't have (using the wrong treatment).

laticauda -- Thanks for the guidance. Based on their website, sounds like you're spot on with their training. Made me a little apprehensive about the quality of response I may get, but hopefully they have a system on their end where they can refer questions to more experienced Disaster Gardeners when needed.

Rob -- I don't think I have any experience with fungus, so to me, it neither looked nor smelled like it (: