Hello, Paul and welcome to Just Answer.
From your description, you could be seeing evidence of an anal gland problem and it would be advisable to have Maggie evaluated in person by a vet. This could be a health issues, if the anal glands are impacted, infected and/or are not emptying as they should, with each bowel movement. Anal glands
The small white growths could also be a result of irritation, like small pimples developed from contact with a rough surface or even an allergy to her litter or anything this area contacts when she sits.
The only way to know for sure what these are, and to have them treated, if needed, is to have Maggie seen by a vet and in this way, you will get a definite diagnosis and treatment (if needed).
If she is eliminating as usual, and eating, drinking, acting normally, you can probably wait until after the weekend to have her examined in person.
I hope all will be well with Maggie!
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