water it only when the soil is completely dry. at least for alot of them and in the winter more then the summer. that is the reason i dont use soil that holds moisture like bark and charcoal. Dont get me wrong the heavy soil works fine some times and if you can restrict your watering to like once a month. but it is a little easyr with really quick draining soil like one part drainage rock one part sharp sand and one part high quality potting soil.
if its not growing it is fairly safe to just not water them. cactus more so then succulents.
also plastic or glazed pots need more heat to dry like 80 f + or a week or so and the succulents dont like that
and judging from the leaves in the plastic tub behind the plant if anything it is to wet if it wanted water the leaves would wilt on the stem. then fall off hard and brown not yellowish
the blue plants look OK i would not water it until it is sunny for most of a week or its time to put it outside.
wet soil can and will do things to succulents that dont really make sense like the leaf droppage.
i hope i was of some help
