I'm also dealing with something that looks very similar right now. Mine is definitely a mold of some kind--it has a mycelium and smells like rot--but I'm still struggling to ID it. One noticeable characteristic is that the fruiting bodies have these hard little balls? It's weird.
I've transplanted the affected plants (into smaller pots because they lost root mass) and replaced as much soil as possible, then inoculated the new soil generously with a broad mycorrhizae mix. This seems to have helped as the plants are growing again, when before they were kind of just slowly languishing.
It's drought tolerant and while the affects are slow I'd say it definitely IS pathogenic, all the plants I've seen that have it have very slowly, but surely, declined in health and a few have finally died of it, their roots rotted.
