How can one determine and compensate for missed fasting days due to ignorance of menstruation rulings, and is it obligatory to feed a needy person for each day?

The brownish discharge (Al-Kudrah) after menstruation is not considered menses if it appears after seeing the sign of purity, based on the statement of Umm Atiyyah: "We did not consider the brownish and yellowish discharge after purity to be anything." Therefore, fasting on those days is valid. However, if the brownish discharge occurs before seeing the sign of purity, it is considered part of menstruation. Some scholars are of the opinion that brownish discharge, whether before or after the cessation of blood, is not considered anything at all. If you wish to make up for days whose obligatory make-up you doubted and whose number you do not know, then fast what you predominantly believe will absolve your responsibility, or what you are certain will absolve your responsibility by fasting it. You are not required to offer expiation along with the make-up unless you were certain of its obligation and delayed it without a valid excuse until another Ramadan entered, while being aware of the prohibition of delaying it.