I watered everything today, and it give me a chance to inspect each plant to see if something new was happening. The Echeveria Setosa Var. Deminuta isn't setting the world on fire and it has had a notch in one side for quite a while. Today as I was watering, I took note that the notch looked sort of like an offset forming. If so, that would be a "good" something new.
And then there is the "bad" something new. The Crassula Capitella 'Campfire' has a bunch of white patches.
First thing I did was remove 'Campfire' from the greenhouse and put it on a vacant shelf in the garage. Upon further reflection, I also parked the Kalanchoe humilis 'Desert Surprise' on that shelf. Its powdery covering looks like farina and is not in patches, but one of the stems recently died and the plant does not look normal. I'm reconsidering that it might be something else. The current working theory is powdery mildew, for sure on the 'Campfire' and possibly on the 'Desert Surprise.' There are some relatively inexpensive treatments for powdery mildew, including a copper-based fungicide or potassium bicarbonate.
I didn't see it on any other plants, except maybe the Crassula 'Coastal Coral.' It has some lower leaves with white rims, a different symptom. So for now it has not been quarantined. Maybe I will haul it in tomorrow just to be safe.