Must a day on which brown discharge was experienced at Maghrib be made up, knowing that it continued until the following day and precedes menstrual bleeding?

Brown discharge, if it occurs during the regular period, is considered menstruation according to the Hanbalis. If you only see it at Maghrib, your fast for that day is valid and you are not required to make it up. It is considered menstruation because it occurred during the usual time. It is considered menstruation unequivocally by the majority of scholars.