What is the ruling on the missed prayers over four days during which the questioner thought she was menstruating, but then discovered she was pure?

It is clear that the questioner is experiencing istiḥāḍah (prolonged vaginal bleeding outside of menstruation) due to the continuous yellowish discharge. She must do what a woman experiencing istiḥāḍah does: wait for the duration of her customary period, then perform ghusl (ritual bath) and pray. If she delayed the ghusl until after the seven days, scholars differ on the obligation of making up the prayers. The madhhab (school of thought) of Shaykh al-Islam is that it is not obligatory, but as a precaution, making them up is a way to clear one's conscience.