Is it valid for me to perform ablution once for Fajr and Subh prayers, and another time for Isha, Shaf‘, and Witr prayers, given that discharges are continuous?

If the discharge is continuous and does not cease for a time sufficient for purification and prayer, then the sister asking the question should perform ablution (wudu') for each obligatory prayer after its time has begun, and pray with this ablution the obligatory prayer and whatever supererogatory prayers (nawafil) she wishes, whether they are before or after the obligatory prayer, as well as the Witr prayer.