Is the action of not performing prayer for fifteen days considered correct in the different cases of menstrual cycle disturbance described by the questioner?

If a woman sees blood, along with any yellowness or murkiness connected to it, for a period not exceeding fifteen days, then the entirety of that period is considered menses (hayd). However, if the duration of the bleeding exceeds fifteen days, she is considered to be in a state of istihadah (post-natal bleeding or irregular bleeding), and she must revert to her previous custom (habitual period). If she does not have a previous custom, she should act based on sound discernment (distinguishing between strong and weak blood). If she cannot distinguish, she should refer to the predominant custom of women (six or seven days). What the questioner did in the first and second scenarios is correct, but in the third, it is incorrect, as she should have reverted to her custom after it was established that she was in a state of istihadah.