Cut the soil with at least 50% perlite (you can alternatively be amused for hours here reading about soil recipes) and water less. If it's just that plant, I'd say something's wrong with it specifically, as the other plants (which need similar care) are not dying, right? All of the plants would benefit from a soil that's much more porous, hence the perlite tip, but they also look like they could use more sun (they'd grow best in full sun, as long as you acclimatize them for 2 weeks or so to the change in sun, lest they get sunburn).

Also, you should handle plants like the one you're speaking of as little as possible by their leaves, which have a bloom on them (like some plums) which helps protect their leaves. Aside from that, the coating is irreplaceable (although part of the plant growing is losing old leaves and growing new ones).

Besides all the things that Cactusmcharris has said. I think the little bugger is a bit crowded. I think we tend to over crowd our plants.

hmm, well I did use a cactus/succulent miracle grow mix? I guess that's still not porous enough. Yes, the rest of my plants are doing well. I have bought that kind of plant many times before and I just always have bad luck. I'll have to replace it with something else now.
Next time I will try more perlite. Could be the sun too, I have them in front of a window but it's not terribly bright.

Echeverias really do want to be outside as much as possible. Miracle grow cactus mix needs an equal part of perlite/grit added to it., But crowding is an issue. Many of the kalanchoe grow up and out. leaning over the echeveria which grows out in a spreading rosette and loves sun. There is a conflict.

I see... this makes perfect sense. Thanks for the clarification!

follow up:
so my plant slowly died, each of the sprouts slowly turned brown/purple until there was nothing healthy left. I'm done with them as an indoor plant. My next question - is the soil tainted now? Should I replant everything else in new soil or is it safe to keep everything in there?

You could try replanting now but there's a chance that with fall coming up, you might not get enough root growth for the plants to re-establish themselves. If you decide to leave it in the current soil, be attentive about letting the soil dry out completely before you water. When you do repot, mix the soil 1:1 with perlite or pumice as others have mentioned. Miracle-Gro "Cactus Mix" is a fiction, it's not at all appropriate for cacti and succulents without something else mixed in for drainage.