Is the brownish fluid that comes after menstruation, accompanied by a small amount of blood, and then followed by blood on the next day, considered Istihada (metrorrhagia) or Hayd (menstruation)? Is the make-up fasting (Qada') that the woman completed after seeing this blood accepted? Is the make-up fasting (Qada') that the woman observed in Shawwal without prayer and worship accepted?

The minimum period between two menstrual cycles is thirteen days according to the Hanbalis, and fifteen days according to the majority of scholars. So, if you saw blood 12 days after the cessation of your previous menstruation, and it is possible to combine it with the previous menstrual period (provided that the total duration of both bleeding periods and the clean interval between them does not exceed 15 days), then it is considered menstruation, and you must make up for the missed fast. Otherwise, it is considered irregular bleeding (istihada), and your fast is valid. Your fast is valid for the day you fasted without praying, but you must repent and make up for the missed prayers, according to the majority of scholars.