I have a few pots of Lithops. They are all in pure pumice and get only bright filtered light for several hours every day. Never any direct sunlight.

By no means am I a Lithops expert but I think those that you focused in on are goners. To me they appear to be fried & dehydrated beyond saving.

Some of the others pictured still look pretty good though. If they were mine I wouldn’t be putting them in any more direct sunlight.

Wait for others to chime in. Good luck with them.

I’m not an expert either, still new actually, but the pale see thru shriveled ones look like they were either cooked or had some rot below soil level. Since you say you haven’t repotted, I assume you haven’t accidentally bruised/damaged their skin to let pathogens in, so it might be either sun damage or your watering.

I know many websites claim that Lithops can take full sun, but that’s usually outdoors with wind and plenty of air curculation to keep them from overheating. I‘ve cooked my share of lithops, and my house is air conditioned to stay at 75F. You say that the damaged ones were closer to the window, so it could be it. Overheating will also start internal rot, and can take a while to see the damage, but will quickly spread after a certain point.

The other possibility is rot from below the soil line due to wetness. Did you check what kind of soil you have? Most nurseries use peat potting soil. Yours looks like vermiculite on top, but does it go all the way through? I pot mine in either pure seed starting pumice or a mixture of mostly pumice and some cactus potting soil, depending on the size of the pot. I can get away with using more water retentive mixes when using smaller pots, like mini bonsai size. Larger pots, I use pure pumice. Unfortunately, rot can set in below and can take a while before you see any damage up top. By the time you see it, the plant is dead.

I’d repot the ones that still look good. You‘ll be able to see if there is any damage. Take out any rotted ones, so mold/bacteria doesn’t spread.

I personally like to pot my lithops above soil level, so I can see their bodies & make sure they don’t stay wet. I only water when the bodies get horizontal wrinkles. The delicate green parts (usually below ground) also get hardened off by the light (changes color to match the top) so the whole skin gets tougher. Mine only get a couple hours of morning sun, rest is bright shade. I’m not an expert at all, but this is how I’ve kept mine alive.

Lithops are generally more finicky than other succulents. When you pot different species in 1, it's a definite death sentence for the more sensitive species because they all require different heat/water/care level.

My top tips to keeping these guys alive.

#1 Plant these bad boys individually in LONG and narrow pots. They do very well burrowing with their deep roots.

#2 Do not move them, they prefer to not be disturbed. Constant lifting of the pots will cause them to stun growth and sometimes die.

#3 Full sun is no problem for lithops, but any hint of humidity will cook them. So unless you live in a very arid zone, be on the safer side, put in very dry soil like pumice or growstones, and place them near ventilating fans or roof areas with high wind and shade.

#4 water through the bottom with a watering tray, this prevents rotting on the stem or root level. This also strengthen roots to burrow deeper.

For those that looks shriveled, sorry to say, those are beyond any help. Those that are splitting are perfectly normal, usually I tend to wait till the outer leaves are dried up before I resume normal watering schedule.

Thanks for this input! I’m new to succulents and am fascinated by lithops. I have had one particular one for about 2.5 months and it appears to just be chilling. Questions: 1) I now realize that the tiny pot I put it in when I first got it is too little for a lithops of its size. Should I be in any hurry to repot it? 2) I had no intent to water it, but a couple of weeks ago it started getting horizontal wrinkles. Because I don’t know its history (when it was last watered), I decided to give it a good drink. It went right back to normal. Today I noticed small wrinkles starting again. Assuming the wrinkling progresses, should I water again at that time?