"White cottony on succulents" makes me think mealy bugs. Try dabbing at them with cotton swab soaked with rubbing alcohol. Soak, then swipe. They should come off, and ... it's been a while since I had to deal with them but ... I believe they should be reddish or orange underneath the waxy coating (this is what you are melting with the alcohol).
If successful, then go ahead and remove the pests from the succulents with the same treatment. If you can, try to isolate the infested plants while you treat them, and set them apart so they are not touching each other -- mealy bugs are crawling insects. You will need to keep an eye on them for emergence of next generation and may need to go over them several times.
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