Was ignoring the blood found after ghusl a mistake, and must the prayers for that month be redone?

It is advisable to ignore and disregard obsessive thoughts (waswas). If a woman performs ghusl after her menstruation, she should not search for remaining traces of blood nor repeat the ghusl. However, if she is certain that blood has reappeared after its cessation, she must repeat the ghusl if the recurring blood has stopped and if its reappearance and cessation occur within a time frame suitable for it to be considered menstruation. If you are certain that blood reappeared after its cessation and you did not repeat the ghusl, then you must perform ghusl if you have not done so thereafter. It is safer to repeat the prayers that were performed without purification, as purification is a condition for the validity of prayer. This is the opinion of the majority of scholars.