I'd say you aren't keeping it warm enough during the day, the plants are natives of the Canary Isles. The daytime summer temperature should be between 20˚C - 30˚C (68 - 86 ˚F) overnight 12˚C - 15˚C (54˚F - 59˚F); 12˚C - 18˚]]C (54˚F - 64˚F) during winter days and no lower than 5˚C (34˚F) at night.

I suspect drainage might be an issue - you appear to have it in a container with no drainage holes, or I'm assuming that because its standing on a surface with nothing beneath. Best planted in something with drainage holes to allow excess water to drain away.

It's not in an air conditioned or heated space, anyway, so there's no way I can change that, but the temperatures you listed are just about accurate for here in the Bay Area, although maybe a tiny bit cooler. It's usually between 60-75 degrees Fahrenheit and no cooler than 54 fahrenheit during summer.

As for drainage, as I said in my post, I water it and let it drain once a week. There is, in fact, a hole in the bottom of the pot, and I always let it drain until it's not dripping anymore before I put it back in the saucer.

Okay, scrap that theory then, lol! How long have they all been in the same pot together?

Another though what sort of compost do you have it in? I've seen them growing in the wild and the soil, to use the term very loosely, is basically sandy with bits of lava and rock. So you need a very open free draining compost. Personally I'd repot with a good inch of pea gravel in the bottom of the pot and then a mix of 2/3rd sharp sand or grit and 1/3rd loam.

Thanks for your advice. I'm not exactly sure what kind of soil, but the "expert" woman at the nursery potted it for me, and she told me she was using some kind of loose gravel like you're talking about. These were all planted together about two months ago. As you can see, the aloe plant rotted and I took it out. I guess once a week watering for it was too much. Any other ideas? Too much water? Not enough water? Not enough sun?

My thought would be too much water and not enough sun... And change the compost.