I am not sure what is wrong with them and would hope someone smarter than I will come along and help out. Not sure if it's a disease or growing conditions not right.

But I will tell you that these plants need a fast draining potting mix, and commercial cactus and succulent mixes are most often too water retaining. Remember these are succulents, they hold a lot of water in their leaves and suffer if they are overwatered or in soil that holds the water too long or even dries out and resists water. The best practice with succulents is to have a fast draining soil, and when the plants are dry, water until the water comes out the bottom of the pot.

If you want to try to save them I would suggest mixing your cactus and succulent mix 50-50 with either perlite or pumice available at nurseries here, not sure what's available for you there. Both pots need to have holes in the bottom so you would want to replace the one without a hole. If you do a repot and notice rotting stems, the plant probably won't make it.

Also, 10ml of water does not sound like enough. When you water you want to give it a thorough soak, until water runs out the bottom of the pot (which is also why having a whole in the pot is so important --so you can water properly!) :)

Eta: just realized that Socks said pretty much the same thing! Oops!

Do you have mites? The new growth looks damaged and distorted. Recommend using a 30x or higher loupe for very close inspection.

I recommend not putting rocks on the top. It can make airflow slower.

Quarantine far from your other plants *immediately*. You need to identify the mite species or type and confirm they are not affecting any other plants in smaller, less damaging numbers.

If only one plant for sure affected, you may choose to destroy the plant or treat it. Treatment for mites is challenging and can be somewhat expensive depending what you use.

If many plants are affected then you may want to attempt treating them. You need to know which mite it is though to use the right stuff and be successful.