Brown vaginal discharge is most often associated with old endometrial tissues. In other words, if your period is late you might get a brown, rather than red, discharge. It could also mean that for whatever reason during your last menses the entire uterine lining failed to make a timely exit. This brown vaginal blood with discharge can also be due to your old blood retained after periods or it can possibly be implantation bleeding in case you are pregnant.
Other causes could be polycystic ovarian syndrome, diseases of pituitary gland, hormonal imbalance of estrogen and progesterone and uterine abnormalities like fibroid and cervical dysplasia.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.