Must a girl who experiences a brownish discharge, and doubts it is menstruation, fast and pray, especially since this condition occurs after her usual days of menstruation have ended?

If a brownish (kudra) discharge, connected to and accompanied by the signs of menstruation, appears before the expected time of menstruation, it is considered menstruation, for which prayer and fasting are abandoned, unless the combined duration of the brownish discharge and blood exceeds fifteen days. The woman remains in a state of menstruation as long as this discharge is continuous with blood and she has not seen any signs of purity. She must make up for any fasting she observed during this period, because the fast of a menstruating woman is not valid.