No fine particles of any kind, they're likely to clog up the mix & impede watering & aeration of roots. Sans are plants unlikely to need special soil amendments. They're one of the few plants I use recycled mix for. The wrinkling is most likely a symptom of plain thirst, has nothing to do w/ root rot. I'd use ordinary cactus & succulent mix, w/ 50% added perlite & pot them up, wait 2 days to water well, 'til lots of water comes out the bottom. Wait a few minutes & pour off the excess water. If you do use the Coir, make sure it's rinsed, I hear it often comes salted & needs rinsing first. Don't know what rock dust is, nor what its purpose would be.

Justine The reason I asked is that soil looks quite wet to me and quite compacted. It would retain too much water for too long, and succulents really don't like that. They need well draining mix, and pots/containers with drainage. 'Moss/greenish part' you removed is not moss, but algae - it grows in moist environment. That is a good indicator of wet soil. Adding organic soil may be adding to the problem down the road. Succulents' natural habitat is typically very lean soil, rocky-gritty, with excellent drainage. It's mostly inorganic. Growing in containers, where the growing area is much smaller, makes drainage even more important. I would suggest that damage on the leaves of your plant is caused mainly by poor drainage. I see you are in location with high temps, so plants could be drying up faster, but drainage is still very important.

If this occurs (with ZZs) when you can still detect moisture deep in the pot with a "tell", you're very likely over-watering or one of the damping-off fungaluglies are at work rotting roots. If it doesn't regain turgidity and plump up within a day after-watering, serious damage to roots has likely occurred due to a prolonged period of dry soul and root desiccation. A high level of dissolved solids (salts) in the soil solution can also cause the symptoms shown. Using a 'tell' Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant. Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor. In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water. Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'. One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue. Al

Thx Socks, for starting the responses. I too thought abt that mix, it looks a bit sandy to me. Is that soil hard to your touch? Agreeing w/ all suggested above, I'd also get some Perlite & mix it in equal parts w/ the C&S mix mentioned above; it needs to be at least 50/50 or the Perlite won't be enough to keep it fast draining. I'd take the wrinkling to indicate thirst, but don't know where you're located. If in FLA, I'll leave it to others for addt'l suggestions. When was the last time it was watered? I'd try a good, deep watering, 'til it comes out the bottom, then wait a bit & pour away any excess.