dormancy or something serious?

[cacti and cacti not]

My dorstenia foetida and gerrardanthus lobatus have experienced some stem shrinking this winter. Is this simply dormancy, or is it a sign of something worse? In addition, my monadenium magnificum is leafless (this I assume is normal, right?).

[kak tus]

Is the stem soft? If so, it could be rot.

[cacti and cacti not]

The stem isn’t abnormally soft. It’s a bit shrunken. The coloration is normal

[Aiko]

I know my Petopentia natalensis shrinks really a lot during its winter dormancy. But I withhold water between around November and April. It can get so soft and wrinkly, one might think it is dying. But after the first watering it plumps up immediately.

[cacti and cacti not]

Thank you everyone. My Gerrardanthus is in fact a little soft, but it isn't rotten soft.