Are brown discharges, unaccompanied by frank blood, considered menstruation and do they affect the validity of prayer and fasting?

Yellowish and brownish discharges are considered menses if they occur during the regular period, or if they are continuous with blood. Therefore, the brownish discharges the questioner sees are not considered menses unless she sees them during her regular period and their duration reaches a day and a night, or they are connected to her regular period without being separated by a period of purity. Otherwise, they fall under the ruling of istihada (irregular bleeding), and her prayers and fasting are valid.