Aparlato, since this condition is occurring to all your plants, the blame cannot fall on something about the individual plants. So.....it has to be something you are doing to the plants...overall. I must ask a question: Are you on a well, and do you have a water-softening agent ---such as salt to make your water less hard? That in itself could be the reason why your plants are suffering. The salt build-up would take time to act on the plants....but seeing as how all your complaints are happening at the same time, I suspect its something that can come about because of something that is being done to all of them.....such as watering them. If this might be the case; I suggest you do a thorough leaching. Sinks, bathtub and such... since these faucets would hardly be OFF the system, you would have to find a tap that is not. Or, gather rain-water---or snow....and melt this. Let the water gain room temperature....then fill a tub or large pot with sufficient water to allow you to immerse the pots entirely in the water. Allow the bubbles to cease. This serves two purposes: It puts water entirely throughout the soil and if there are any bugs in the soil, they would have to come to the surface to breathe. There, you dispose of them. It is also a very good way to thoroughly rid the soil of harmful salts---either from too much fertilizer...or possibly as I suggest...as on a water-softening system. Treat this as a watering. Allow full drainage and put your plants in their respective sun. If you feel it is necessary, you might decide to change the soil instead. A fresh potting soil with lots of vermiculite. Just be sure to not use such softened water from any of the taps on the system. Usually a home will allow a tap or two to be OFF the system....for watering the lawns, washing the car...etc This could be thought of....gather water there and hold for plant use. If you are not on a water-softening system, such a happening to many plants at the same time I suspect still you are overwatering---perhaps you water as per schedule...and not according to how the plants need watering Your plants....succulents, hold water in their leaves as a resevoir and can take dry periods for a time. As long as they aren't allowed to go completely dry, they should be able to withstand some dryness without being badly affected. You might, when the first sign of limp....or wilt occurs, give your plants a thorough watering.....to the drainage point. Then dump the excess...never leave your plants sitting in such drainage for any extended time. Then allow them to dry down a bit between watering.....then water to drainage.

If the base is squishy, it's rotting and you'll have to take a cutting and re root it. Take a wooden skewer or chopstick and put it in the soil for a few minutes. Pull it out to see it if it is damp. If it's damp, don't water. Your plant needs more light. Do you have a window which gets more light, like south facing? If so transition slowly into that light. If you want to put more effort into it, get a bag of cactus and succulent planting mix and a bag of perlite or pumice. Mix 50-50, repot your plant. Don't water for a day or two. When you water, let the water run out the bottom hole, I don't just water a little bit. your plant needs bright light to full sun and fast draining soil. The morning sun it's getting, it needs all day.

The stem could have just dried up. Or, it may have been rotting first and then dried up. Can't really tell. Soil it is in looks like peat, and could have been kept too wet or too dry. Not sure if you can save any of it. You could cut off those still green & live-looking pieces. Let them callus for just a while, then stick in a very well draining mix. Not peat. Many ppl use mix of coarse perlite and Cactus & Succulent soil in 50/50 ratio, maybe you should try that mix. I wonder about white area on one of the branches - circled in red:That may be just salt deposits, but could be mealy bugs too - I can't tell from your photo. See if it will wipe off easily, using paper towel or cotton ball. If bugs, you should wipe it off with something moistened with rubbing alcohol. Any pot used for plants should have drainage holes - can't tell if yours does or doesn't...

That looks like Aloe juvenna, very easy plant to grow. Cuttings grow easily; I posted some photos on this thread I can't think of the reason for leaves to be wet? Did she pour water over? or it got rained on? If plants keep rotting, it must be watering issue. Soil plant is in looks like peat, not really suitable to grow succulents. Cuttings, just potted: