Stapelia tips shriveling

I don't know those plants well, but my first guess would be the water. What is the source? Municipal water? Well water? Softened? Is it winter where you live? How often are you watering?

Municipal water, not softened, varies in quality but tends to be on the hard side. It's winter, I'm watering it lightly once a week, it's potted in a mixture of about 50% commercial potting soil and 50% sand.

Some plants are sensitive to levels of chlorine that you and I don't notice. The best thing for house plants is to age the water in an open container for a couple of days before using it. Chlorine will dissipate by then.

This site's got some interesting tips about avoiding fungal issues around the stems, but not much about how to recognize the problem.

All leaves or just younger or older ones?

First thought for me when I see leaf tip death is usually salt burn. How long has it been in the pot? Have you leached the soil? Use much fertilizer? If you let some dry, does it make a nice white or yellowish crust on top? Cu deficiency is another possibility, but a real long shot -- and Cu is toxic enough I would rule everything else out first, and then supply it as compost or well-rotted manure.

Mostly older ones.

About a year.

No.

No.

There is a small amount of crust. I have some crust on a lot of my indoor plants, I think it's from the water supply which, as I've said, tends to be on the hard side. I've never had it result in leaf burn in a plant so young though (I only got the Stapelia last year), and usually repot before it becomes a problem. I've also never had leaf burn on succulents, but I suppose there's a first time for everything.

The site I pointed out earlier said that in winter (short days), water less, or maybe not at all. If it's winter where you live, wait this situation out. When the plant seems to be making new growth, collect some rain water and and pour LOTS of it through the soil. Do it over the sink so the water can drain out thoroughly. Or, if you don't want to wait, repot with fresh soil, melt some clean snow, and use that to water the plant.