Is it obligatory to make up the fasting of the seven days during which there was only brown discharge before sunset and no blood, followed by bleeding due to a miscarriage?

If the discharge is brown, it is not considered menstruation. The fasts on those days are valid. If the age of the miscarriage is eighty-one days or more, it is considered nifas (postnatal bleeding). If the age of the miscarriage is less than that, it is istihada (irregular bleeding), and it is not considered menstruation unless it coincides with the usual time of menstruation.