We need more info and pics in order to help. What pot is it in? Has it got holes? What soil have you used? Are they all the same type of plant? How often have you watered and with how much water? Is it in full sun, if not where is it? Plus anything else you can think of!....and the pics! My guess is a bagged cactus/succulent mix and too much water....I hope not though :)

Gill UK

Potting soil is not good for succulents. Using large rocks like ones in the photo won't help the drainage since they are too big. It would help if you can find grit - the size of approx. that of aquarium gravel. And if you add same amount of perlite or pumice, you could have very good potting mix.

I would think that they are over watered, there is rot visible.

Rina, just as I sadly predicted eh? Great minds. I do wish we could have a sticky to try and encourage people to switch their peaty organic commercially gagged mixes to something that will really help their plants thrive. It's such a shame when all these plants die.

jenny, hopefully with a more suitable fast draining mix you will be able to save some of your plants, but you need to act asap.

Gill UK