Interesting that the other Echeveria seem to not be getting enough light. What are they doing that makes you think that? Have you had them longer than the Perl? I'd consider a plant you've had for just 2 months very new. In just two months, this time of year, a winter-dormant succulent like Echeveria probably hasn't had time to establish a good root system in the new mix you've put it in, so it will be very susceptible to drought until it's established, which probably won't be until midsummer for this species. My own Perl opens up flat for more light, and closes up like its trying to make a fist when it's getting too much direct sun for the amount of water it's getting. It could be that yours is too dry for that amount of sun, especially since it isn't yet established, and appears to be planted in gritty mix (Al's recipe?). In my experience, gritty mix dries dangerously fast. In 60 degrees and partial shade in western Oregon, I have to water my gritty mix plants at LEAST twice weekly. It is quite a chore to keep them all watered in such a porous mix. The nice thing about grit is that it's pretty much impossible to over-water a plant, even a succulent. It's very easy to under-water them though. Because of this, I'd recommend more frequent watering. You can also check the grit by pouring some into your hand to see if it's dry. You might even pour off enough of the top of the soil to get a look at whether it has any established roots. I'm betting it doesn't. I presume you washed all the old soil from the roots before transplanting it, right? As long as your mix is porous (water pours right through), and it has good drainage holes, water away. You might also provide a little shade until it's established.

Using mix made of grit, perlite, scoria, pumice, turface (and some other ingredients) - few of these ingredients will make well draining mix. Here is some interesting reading about soils and includes good photos: -please click here- Itis quite a bit of reading, but it will help anyone to understand why and how to make same or similar potting mixes.

While I agree with garret about rot starting from the bottom, I still believe the watering too much contributes to the problem. I think it makes plants much weaker and much easier to succumb to either bugs or diseases. 2nd plant shows very yellow and 'plump' leaves - I would think they are water logged = too much water/water retaining soil. But there is a small chance that it could be affected already by fusarium from other plant - one of the symptoms of it is yellowing of the leaves. 1st plant shows blackening of leaves but that is likely from the problem just below.

Here is a pic of my sick Agavoides. Same thing happened with mine the water wasn't draining. Stupid pot;)! It's lost some of it's size because I had to remove a bunch of soggy leaves:(. It started getting a couple yellow leaves like this. So I pulled it out of its pot asap! I found damp soil at the bottom:(. It was healthy one minute then started going south quickly. I think it should make a turnaround. Luckily it still had some roots:)! Here are some other Agavoides I have. I think what was once my biggest is no longer:). I keep mine on my porch so no direct sun. So that's why they're all green:). An Agavoides Ebony that is clearly not getting enough sun. Today is the day I will start acclimating him to more sun. So he can get those dark edges:). A little story with this guy. A couple years ago we recieved hail for about 30 seconds. Let's just say ice got stuck in between some leaves. So my Ebony began to rot. It's been two years and I think he's in the clear. I've kept him in the shade while he grew. I had to remove sooo many rotten leaves. The hail made him go from about 8 inches wide to probably about 4 inches wide. Last thing. Sorry for the overflow if Agavoides. I just think they're so pretty:)! One of my favs my Agavoides crest:).