Consider writing an addendum if you have additional information to share not already covered by other application components.
An addendum is an optional opportunity to address any irregularities or unique circumstances the admissions committee might find in your application materials. Reasons to write addenda might include course withdrawals, poor grades, lower than expected graduate school admission test scores, judicial matters, pressing health issues that have affected you academically, etc.
You might also choose to write addendum regarding any issues around diversity that you feel have not been addressed through your application materials.
The schools you are applying to should provide you with the format they want you to use for any addenda you choose to write.
You want to keep addenda concise enough to acknowledge the issue and give the reader a basic understanding of the situation. You do not need to go into detail- speak broadly and matter of factly so the reader has an idea of the circumstances but is not reading anything confidential. Express what you have learned from the situation, and how you are handling the issue(s) moving forward (if applicable). Ensure everything you write is written from a professional perspective to demonstrate maturity and resiliency.
Be prepared for any questions regarding your addenda during potential graduate school interviews.