Ask-a-Dave's-Gardener: Can\'t identify disease/pest on lapidaria , 1 by MistyN

MistyN wrote:
Hi, I\'m hoping someone can help me figure out what\'s going on. About ten days ago I had a minor mealybug infestation which was treated promptly and successfully with alcohol followed by systemic imidacloprid. At the same time, I found these lesions on the lapidaria margaretae. They do not rub off with firm pressure, damp cotton swab, or firm pressure with a cotton swab soaked in 90% isopropyl. The epidermis must be scraped away to remove *any* of this.
Under a loupe, the lesions have a bumpy/powdery surface, irregular tan margins, and each individual spot has 1-2 small tan bumps that can be felt; scraping one off is what left the pit seen in the photo.
They continue to grow in size and number, and now I\'m seeing tiny tan spots on a few other succulents nearby, so I sprayed everything with alcohol and quarantined them all separately.
I have spent hours researching and can find nothing that precisely matches this description *and* which is listed as a disease of succulents. I\'m hoping someone here with more experience might recognize this and clue me in, because it\'s driving me crazy!
Thank you so much for your help.