Is the yellowish discharge that preceded menstruation and continued for five days considered menstruation? And are breaking the fast and fasting after it valid? And is the brownish discharge that appeared fifteen days after the beginning of the yellowish discharge considered menstruation or istihadah (irregular bleeding)?

It appears that menstruation is the usual blood, along with any yellow or brownish discharge that is connected to it (the last five days). Any brownish discharge that preceded this is not menstruation. The days on which one broke their fast must be made up. A ritual bath (ghusl) is obligatory after the cessation of the yellowish discharge connected to the blood. The days of bleeding and any connected yellow or brownish discharge are considered menstruation, as long as it does not exceed fifteen days. If it exceeds that, the woman is in a state of istihadah (non-menstrual bleeding) and must refer back to her previous habit, and anything beyond that is considered istihadah.