What is the ruling on the prayer and fasting of a woman who suffers from an irregular menstrual cycle, where it sometimes comes early, accompanied by brownish discharge before it, causing her confusion regarding the validity of her acts of worship?

If brown discharge appears fifteen days after purification from the previous menstrual cycle, it is considered the beginning of menstruation. This is because it possesses the characteristic of kudrah (brownish or muddy discharge), and kudrah occurring within the possible time of menstruation is considered menses by many scholars, especially if blood follows it. The correct view in our madhhab is that it is menses during the time of its possibility, and it is not restricted by the usual habit. This is what Al-Nawawi stated and quoted from Rabi'ah, Malik, Sufyan, Al-Awza'i, Abu Hanifa, Muhammad, Ahmad, and Ishaq. As for what a woman sees of yellowish or brownish discharge before purification, it is menstrual blood according to Malik, and similarly if she sees it at the beginning of the menstruation period without any prior blood.