Wow, that's an intense black. How much have you been watering? How do the leaves feel? Soft or firm? Can you describe your lighting situation? Was it planted? And if so, in what medium? There are a couple leaves turning yellow and transparent which indicate overwatering but the black leaves look good besides the fact they are black. Sorry to respond to your question with more questions but more info is needed.

That is very strange I've never had that happen. Are the leaves soft and mushy feeling? How cold is it where you live?

Thank you for the response!

I havent been watering much, since the roots just started coming out. The soil has very good drainage, although i mis my own i am very sure the drainage is good.

The black leaves are firm, like healthy leaves. The yellowing/dying leaves are just that way because its at the bottom and its natural for it to die right?

I live in the philippines. My plants are positioned where they get morning sun.

Thank you Patrick for the feedback! L

Wow, that is pretty freaky.

Looks to me like the cuts you did previously did not remove all the sick stem. Seems to me the rot was already up the inner stem, waiting to appear in the leaves. I have many times had rot appear overnight like that, was just inside waiting to come out.

"inside waiting to come out"

Whew! Sounds evil... lol!

Evil, well I live in the SF Bay Area like you....rot, slugs, mealy bugs, they are all out to get us, evil bastards all. Now I have bud worm moving in, aghck.

You mean, even if the cut looked clean this could happen? Oh no... thank you lisasfbay

My succulent did the same thing. It just turned black overnight. Gnats used to be swarming but I got rid of them. All of it turned black though and it is dying but nothing happened with my other succulents or plants for that matter.

I would remove one black leaf and one healthy leaf. Then cut them in half along the vertical and examine what they look like inside. Maybe take a photo of that for us.

Black has to be some kind of mold or fungus and it is weird for it to happen quickly.

Is there any way that half the plant might have been exposed to microwaves or some other kind of extreme radiation or heat?

One leaf of my echeveria also turned black. Likely water got on the leaf.

I removed the leaf with a pair of tweezers and sprayed the plant with 70% rubbing alcohol. Still keep my fingers crossed.

I have never taken it out of the room it is in and I'm very sure it has not been exposed to extreme radiation or heat

Happy 2020!

Also, I have a lot of other succulents in the same room, and none of the others got infected and black, even though I water them all evenly.