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It looks like it's in glass? No drainage holes? If there's no drainage holes I would pull it all out and look for black mushy roots and remove any roots that look that way. It needs light. But you need to acclimate it first. (Only if you're going to put it outside) which succulents REALLY need so they don't get leggy. At the very minimum the soil should be 1/2 cactus soil 1/2 perlite. Hope this helps

You have multiple issues going on here; the leaves should not be falling off like that.
As LilBit said, it appears to be a glass container and if there are no drainage holes that is your first problem. The second issue is your soil looks very peaty, like a regular bagged potting mix. Succulents need very well-draining soil. A simple fix to get you started is to buy a bagged succulent/cactus mix and add 50-70% perlite, depending on how humid your climate is. For the long term, you may want to consider using a gritty mix (you can search on this forum for recipes). When you water the plants, the water should flow out immediately through the drainage holes.

The next issue is your plants are etiolated, or stretching for sunlight. Succulents are generally not indoor plants, but can sometimes be grown in south-facing windowsills (assuming you don't have any trees or anything blocking the light) or under T5 fluorescent lighting. Because these plants have been without sun for so long, they will need to be acclimated over the course of a couple of weeks to more light.

Finally, one of your echeverias (the fuzzy one close up in your second photo) is a bit perplexing. Normally rot coloration starts toward the stem end of the leaf, rather than from the outward edges like on your plant. It's possible you have a fungus going from the excess moisture.

The first thing to do is remove all of your plants from that mix right away. Take a look at the roots; if there are very few and/or the plant stems appear brown at the base, they are rotting. If that is the case, which I suspect, you will need to cut the plants with a sterile knife above any discoloration until you see only green, healthy flesh. The plants will sprout new roots in time and can be re-planted into a more suitable potting mix. All of your plants, even if not currently rotting, should be taken out and allowed to dry out a bit. Don't re-pot them until you are able to get your hands on a pot with a drainage hole and a well-draining mix. Succulents can live outside of soil for months, so don't worry about leaving them out too long - they will be happier that way than in the moist environment.

Also, these are succulents, not cacti :) I hope this helps, and good luck! I'd love to see an update later if you decide to go through all the steps and keep the plants!

What the previous posters said, repot, but if you are in Southern California, it will be perfectly happy, probably happier in the ground (morning sun, afternoon shade) unless you are up in the mountains.

Thank you, LilBit, spapa, and hoovb! I really appreciate the comments! You are right, it is a glass container with no drainage holes. I will relieve my plant from that moisture. Also I do live in Southern California, so hopefully the sunlight will help.

I plan to:
1. Remove it from its mixture
2. Check its roots for rots and remove the reddened parts
3. Acclimate it to sunlight over a few weeks
4. Get a proper gardening pot with drainage holes, and purchase some right mixture as suggested
5. Put it on the balcony (East-facing... I think?) where hopefully the intense Southern California sun will make it happy.

Although it seems to be a lot of work, I will do what I can to save my succulent :) Thanks again for the detailed & helpful suggestions.

This post was edited by elza99 on Sat, Oct 11, 14 at 1:04

elza, that sounds like a good plan! It can be a lot of work, but once you figure out their needs you'll be good to go. I remember when I first found out about succulent soil, light, etc. needs I already had 20 plants from IKEA - new pots and soil for everything in the dead of winter was a pain!