Is the fast considered sufficient if a brown discharge occurred before Maghrib while making up for a Ramadan fast, and continued for three days, followed by the normal menstrual period?

These discharges are the "kudrah" (turbidity) or "sufrah" (yellowness), and they are not considered menstruation unless they are connected to menstruation and accompanied by menstrual pain such as cramps and back pain. If they occur in this manner just before sunset, you must make up that day.