Purity: Transition from Excessive to Medium Istiḥāḍah
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 421:
If the excessive istiḥāḍah of a woman becomes medium, she must do the things required of a woman with excessive istiḥāḍah for the first prayer; and for subsequent prayers, she must do the things required of a woman with medium istiḥāḍah. For example, if before ẓuhr prayers her excessive istiḥāḍah becomes medium, she must perform ghusl for ẓuhr prayers; and for ʿaṣr, maghrib, and ʿishāʾ prayers, she must perform wuḍūʾ only. However, if she does not perform ghusl for ẓuhr prayers and she has time only to the extent of performing ʿaṣr prayers, she must perform ghusl for ʿaṣr prayers; and if she does not perform ghusl for ʿaṣr prayers either, she must perform ghusl for maghrib prayers; and if she does not perform ghusl for even those prayers and she has time only for ʿishāʾ prayers, she must perform ghusl for ʿishāʾ prayers.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)