Baja_Costero said:Did you get the plants bare root? How were the roots when you got them? Did you water right after potting them up? Did you look closely at the stem to see if it was soft or brown?
The more light, the better for indoor Echeverias.
Baja_Costero said:Waiting a while after potting them up (a few days to a week) is best to be on the safe side. Your watering interval sounds about right (see if you can poke your finger into the soil to see how the moisture is below the surface, and wait until it's almost dry or dry down there).
Sudden death with these plants typically relates to rot getting into the stem, either sideways from water trapped in between the leaves, or upward from the roots (often too much water, or watering too soon after root damage). The changes are not often evident until it's way too late. Leaves may fall off for no reason, or start going soft. It's usually pretty obvious from a close inspection whether the stem has rot in it, so you can rule this possibility in or out if you can look carefully, especially at the base where the stem hits the soil.
Water deprivation on the other hand tends to be a grindingly slow, bit by bit process where the plant starts looking deflated everywhere and then begins to extract water from the lower leaves, dropping them one by one and shrinking the size of the rosette as a result. This process might take months or even years to reach a final conclusion. It does not typically result in the plant dropping plump, healthy leaves but only dry, dark, dehydrated ones.
Echeverias will sometimes go through shock when they have been bare-rooted and put through the mail, or otherwise manhandled invasively. They will sit there doing nothing for a while before they decide whether they still have zest for life. They may drop a few totally healthy leaves. I would expect this sort of thing as a matter of course, but it's nothing like the sudden decline you are reporting. The key is to provide strong light at this point and water only when the soil is going dry at depth.
Are you using fast-draining soil, like regular potting soil (I think you call it compost over there) mixed with an equal volume of perlite, pumice, or gritty equivalent? These plants like a nice airy mix and they resent it when the soil retains too much moisture. Do your pots all have holes at the bottom?
Baja_Costero said:The mix and the pots sound great. You might pass on variegated plants like Compton Carousel until you're more confident you can give them a good start (the higher price relates to rarity but also to some extent degree of difficulty). When in doubt, acquire new Echeverias during the brighter months (now would be a great time). December is about the worst time unless you can provide lots and lots of light (like we can here) ... the lower light and shorter days are not great for succulents.