Is it permissible to perform ablution without changing clothes after a discharge, and is it necessary to repeat ablution for Fajr prayer if one performed ablution a short while before it for Qiyam al-Layl?

Vaginal discharge is pure but nullifies ablution. It is not necessary to wash clothes or perform istinja’ (washing of private parts) because of it; rather, only ablution is required. If the discharge is continuous, then perform ablution for each prayer after its time has begun and pray the obligatory and supererogatory prayers with this ablution. You must perform ablution for the Fajr prayer after its time has begun, even if you performed ablution for the night prayer.