Welcome to health care magic,
Thanks for your query.
There are several reasons this could be happening to you. In may be due to Bacterial Vaginosis
but it could also be caused by a wide range of other things.
Vulvovaginitis is the most common cause of a brown vaginal discharge
. It is caused by several things like Yeasts, bacteria, viruses and some sexually transmitted diseases
And it could be like spotting.
Wait till your periods start.If you get this problem again then consult a gynecologist.Sometimes it is normal before the periods start.