All succulents need well draining potting mix, and sand is usually NOT recommended unless it is pretty coarse, often referred to as Horticultural sand. If you are using fine sand (kind that would fall thru sieve), your mix could be to compacted, and drainage impaired. You need to be very experienced to use sand, and IMO - mostly for cacti. What else is in your mix? If I may ask, who recommended sand to be used?

Your pots are quite large for being filled with mix that may not drain well.

Most succulents need good sunlight, but they need to be acclimatized to it. If you just put them into god sunlight suddenly, they most likely burn.

Thanks Rina! Sorry, to clarify, I used a commercial premade cactus mix -- I didn't add any sand to it myself.

Many pre-made mixes are far from what is being advertised, unfortunately. It is difficult, especially for ppl getting succulents first time, to buy a good mix. I never used any, but ppl who do, amend it heavily. They use perlite or pumice, in approx. 1:1 ratio.

Pls. check your existing mix to see how dry or wet it is. Use a wooden/bamboo skewer, or chopstick, thin wooden dowel or pencil. You could stick any of them deep inside of pot and leave in for few minutes. Check if wet or dry upon pulling out.

Further to Rina's advice above, about pot size. The way to judge what size pot to use is to chose a pot only ONE or TWO INCHES LARGER than the rootball. Otherwise there can be drainage problems leading to root rot.

If you're new to plants & succulents, you may do better using unglazed, terra cotta (clay) pots. I don't mean to add confusion, but succulents have somewhat different requirements than houseplants many folks have which are more tropical.