What is happening to my succulents?

In the last month I've noticed most of my succulents are suffering from one (or more) of the following:

-Sagging/limp leaves.
-Bleaching.
-Leaf loss or weak attachment to the stem.

I've read it could be over-watering/under-watering - too much sun/too much shade.

Could someone shed some light (no pun intended) as to why they've suddenly changed? What can I do to bring them back to their former glory?

I've also attached a photo of my sole healthy succulent (in the same planter). Why is this one so healthy, while all the others wilt?

The only thing I can think of is different requirements (though, labeled the same). Should I separate & repot?

How often do you water them?

How much light do they get?

have you made any changes recently? what fertilizer if any have you used?

Does the water drain out the bottom? and then soak back up or can it fully drian out? Some times salts can accumulate especially in pots that do not drain.

As the day length changes the plants may change how they live.
When the days are long they may grow the most, and the warmer weather evaporates the water from the soil faster.
As the days shorten the plants may not use quite so much water, and the water does not evaporate as quickly.

So, for 2 reasons, my first estimate is overwatering.
Solution: Allow the soil to dry out more between watering.

Are these in some sandy, fast draining soil? Might have been labeled cactus mix or something similar. Or, if you made your own, did you add perlite, sand or fine gravel?

Thank you for replying!

-I did make my own mix. They sit in about 3 inches of soil, which is comprised of a 50/50 mix of Miracle-Gro Cactus Soil & Perlite. It's a shallow vinyl planter with (what I believe is) adequate drainage: 2 holes per sq inch.

- During the 100º+ summer, I watered once/week or every other week. Only watering when the soil was completely dry (almost dusty). Since it's cooled down, I have cut it down to 1x/month or so.

- They get about 2 hours of direct sunlight each morning.

- I DID move them a few feet closer to the house, protecting them from the rain & roof run-off. It didn't significantly reduce their sun exposure, but they are getting a little less direct sunlight than before.

- I have not used any fertilizers.


I forgot to mention:
It's getting cooler outside. Should I bring them inside (even with the low light indoors)? It's getting down around 50º at night, and I'd like to give them time to recuperate before putting too much stress on them. Thoughts on how I should proceed?

Also, my Perlite has turned brown (as seen in the photos, above). Is that normal? Or does that signal a pH imbalance in the soil?

Thank you again for your help!