Hi, thanks for using healthcare magic
Brown discharge may be due to infection, slight vaginal bleeding or contamination with faeces.
Since you are not currently sexually active then infection is not likely. The brown discharge may have been slight old vaginal blood and may have been a lighter than normal period.
The causes for delayed period are: stress
but you indicated that this not a problem for you, inadequate nutrition, excess physical activity, polycystic ovarian syndrome
, abnormal levels of thyroid
hormone or prolactin
You can consider monitoring to see if your next period is normal and if not then visit your doctor for an evaluation.
I hope this helps