Is it necessary to repeat Istinja and Wudu upon the discharge of sticky secretions after relieving oneself and performing Istinja, either before or after Wudu?

Natural secretions (vaginal discharge) are pure, but they invalidate ablution. If you doubt their emission, do not pay attention to the doubt, and build upon the original principle, which is non-emission. If you are certain of their emission after performing ablution, then perform ablution again for prayer, and you are not required to perform istinja' (washing the private parts).