Is it obligatory to perform ablution for every prayer when there are vaginal discharges that often appear upon examination, and the exact time of their emission may not be known, and is this considered سلس الإفرازات (incontinence of discharge)?

You are not obligated to search for discharge before the prayer time. It is sufficient for you to assume the default, which is that nothing has exited. You are not prescribed to repeat the prayer as long as it is valid, and searching and scrutinizing purity is an act of excessive burden (takalluf). If the discharge stops for a period sufficient for Wudu' and prayer, then the ruling of a person with incontinence (sahib al-salas) does not apply to you. However, if its cessation is not regular, then it is considered incontinence.