Some pictures of the Pachypodiums that are leafing out right now, way earlier than last year. This has been a warm winter, but I also started acidifying the water, and I think that may have been the deciding factor. They receive full sun for most of the day this time of year (S exposure).
Growing these plants is a little like surfing. When they go leafless, you have to float for a while and wait for the next swell, giving the minimum irrigation. But then when they decide to go green, they get way more thirsty, and you have to start pouring on the water to keep the plant going. At some point when they're making new leaves, I imagine the roots down there underground also budding and sprouting and expanding.
In the past I have had plants start leafing out on me and then stall out completely because I was watering them like cacti, letting the soil go too dry for too long each time. Very frustrating. Now I'm much more free with the drink when the plants indicate they are ready for it. They still dry out most of the way, but not all the way, and that seems to make a big difference.
Pachys leafing out
They look lovely. Looks like you've found their sweet spot.
Those plants are a few years old, don't know exactly. I've had most of them for 2-3 years.
Don't know what's going on with your plant. Is the stem still hard?
The stem is definitely not mushy, maybe just a little softer than other healthy ones.
I don't know then. Give it some sun protection and water conservatively. See if you can get a look at the roots without causing damage down there.
It's hard to tell from the pictures, but it looks like there's not a lot of rock in the soil. That may be related to health of the plant. I always add a good amount of pumice to the mix so it's super fast draining. Whatever you have available, perlite and lava rock work too, say 25-50% by volume.
I was going to say the same thing Baja. The soil does not look like it has enough fast draining material. I would definitely remedy that when you check the root system. Maybe the roots have started to rot and will not support the plant.