Does the blood that is discharged from me two or three days after the cessation of menstruation, and which continues for five or six days, invalidate the fast, requiring me to make up the days, or not?

The brownish discharge after menstruation is called "kudrah." It is considered menstruation if it occurs during the usual period or immediately follows the blood. Otherwise, it is considered istihadah (definition) (non-menstrual bleeding). So, if a woman becomes pure, either by dryness or by seeing the white discharge, and then sees the brownish discharge two or three days later, it is istihadah, and its ruling is that of a pure person; she prays and fasts. The majority of jurists hold that a woman experiencing istihadah must perform ablution for each prayer after its time has entered.