Is blood that comes nine days after the previous menstruation, and has the known characteristics of menstrual blood (thick and tending to be dark), considered menstruation or istihadah, knowing that it appeared due to psychological stress and disturbances in eating and sleeping?

If blood appears nine days after purity following the last menstrual period, it could be either menstrual blood (hayd) or irregular vaginal bleeding (istihada). It is considered hayd if the total number of its days, combined with the days of the last hayd and the nine days of purity in between, does not exceed fifteen days. It is considered istihada if its flow continues such that the total number of days of the last hayd, this current bleeding, and the days of purity in between (the nine days) exceeds fifteen days. In this case, it is deemed istihada blood, which does not prevent fasting or prayer.