What is the religious ruling on seeing drops of blood after a full day of fasting and purification from menstruation in Ramadan, and must this day be fasted again?

If a few drops of blood appear after the usual end of menstruation, they are not considered menses unless they recur three times, or if the bleeding stops and then resumes before the usual period ends. If it is not menses, your fast is valid. If it is menses, your fast is considered complete according to the Hanbalis and Malikis, whereas the Shafi'is and Hanafis consider these days as part of menstruation. Making up for this day is more cautious.