What is the ruling on the yellowish discharge that continued for more than 15 days after the blood stopped in the period of irregular menstruation?

Yellowish or brownish discharge after purification is not considered menstruation and does not prevent prayer or fasting, based on the statement of Umm Atiyyah: "We did not consider the brownish and yellowish discharge after purification as anything [of consequence]." At that point, everything required of a ritually pure woman becomes obligatory for her, and everything permissible for her becomes permissible for the pure woman, with the caveat that its discharge nullifies ablution.