Is the appearance of brown or dark yellow discharge during an irregular menstrual period considered the beginning of menstruation, thereby necessitating the cessation of prayer and fasting, and what is meant by "the usual duration" in this case?

The preponderant opinion is that brown discharge (kudrah) is not considered menstruation unless a woman sees it during her usual menstrual period. If she sees yellowish or brownish discharge during her customary days of menstruation, it is considered menstruation. However, if she sees it before or after these days, and after the blood has stopped, it is not considered menstruation. As for blood that a woman sees after fifteen days have passed since the cessation of her menstruation, it is considered menstruation.