Are they hard? It may be oedema?

Could be scale insects. They have a waxy, hard coat. Scrape one off. There are methods to get rid of them, but when a plant gets scale, I toss it and go shopping for a new plant. Not worth all the trouble, and that particular kind of plant is easily started by rooting a leaf in fresh soil.

Your Easter Cactus (I can tell by the shape of leaf & the hairs) has a fungus, has happened in the past on mine too. I was told by a horticultural friend to spray with a fungicide and dispose of those worst fungus dotted leaves. I used the Bayer 3 in 1 as that's what I already had on hand. Often 2 or 3 treatments are needed (read the label). It happens when they stay too wet too long. For some reason Easter Cactus are extra susceptible to this, so I try to keep the leaves dry or water in the morning so it has time to dry quickly in some sun.

Some of those brown things do look like scale (second picture, at the top), maybe along with the fungal infection. And scale does leave a hole where it has eaten the leaf. In any case, i would throw out the plant and start fresh. It's not like it's a huge, beautiful plant with sentimental value. It's sickly and it's a houseplant. :)

Also, i see lots of people post problems who have those pebbles on top, so I wonder what they are contributing...

There is very easy way to determine if plant has scale or not: take a q-tip; moisten it in rubbing alcohol. Smear directly over the questionable spot. If a bug - scale - it will come off easily since rubbing alcohol will kill it on contact. I have experienced scale of few different plants (some succulents and also non-succulents), and never found a hole left after bugs were gone. I treated it with rubbing alcohol, keeping plant out of the direct sun while treated. It has been some time since I saw scale last time...

Having approx. 300 pots of succulents and using gravel for top-dressing on all, I never had problem with it. Perhaps some ppl have problems. Problems are usually caused by the potting medium under the top-dressing.

If there is extensive infestation, it may be good idea to get rid of plant - sometimes. But one should be sure what the problem is before discarding it. I see only very few spots, scale multiplies if not taken care of.

Hillary

How long since you noticed spots? Where is the plant kept (indoors? outside?) and how muh-how often do you water it?

There is a chance of mechanical damage too - but that is usually bigger , just as visible on coupe of pads in pic #2. Do you know what happened there? (not a problem, just wondering).

ETA:

I found a jade with round spot that some may think it is scale. It is oedema. I wiped it with rubbing alcohol, but it doesn't come off. I scraped it, and it left indentation - just as I mentioned above. It doesn't look exactly same right now as marks on plant posted by Hillary, but it is fresh - I just did it. Here is the leaf 'before' and 'after':

My plants have these little bumps and depressions and I don't concern myself with it. I guess that plant, based on its leaves is S. xbucklyi, not R. Gaetneri.

Hillary

That is interesting. I can't tell if the 'color' is because of blood. If it was a bug, that's what it would be. You also said there was 'slime' over it, and I don't remember seeing that on any scale - but, there are many species of scale. If scale, there isn't that many and could be treated with rubbing alcohol. If it is fungus as Nancy suggested, fungicide should help.

If the soil is still wet, it is most likely not draining well. Most ppl here don't recommend using sand and would leave it out completely. Gravel or small rocks are better for top-dressing than sand IMO. Plant may be better in a mix of C&S soil and coarse perlite. Using a bamboo skewer or chopstick inserted deep inside of pot helps to see how fast potting mix dries - it may work even better than moisture meter :) And making sure there are drainage holes in the container.

Another sign that your soil doesn't drain well enough are fungus gnats: they like wet conditions. So if you had them (or still have them), repotting plant into better draining mix would make sense.

It may not be best idea to propagate succulents in water. Some ppl do, but succulents are low-water plants and often will rot. I never propagate them in water (and have many plants grown from leaves or stem cuttings...I would say that probably 30% of my succulents are grown from cuttings by me. I have many hardy succulents too, and none have been propagated in water...