Is ghusl for janabah sufficient if I believed that the yellowish discharge was istihada and I prayed without performing ghusl for it, then it became clear to me that it was connected to menstruation, and I had already performed ghusl for janabah after the prayer?

If the yellowish or brownish discharge occurs during the menstrual period or is connected to the blood, it is considered menstruation. However, if it appears after purification (Tuhr), it is not considered anything.

One ghusl (definition) (ritual bath) is sufficient for both menstruation and janabah (definition) (ritual impurity requiring ghusl) if the woman intends to lift both impurities simultaneously. This is the view of the majority of scholars. Similarly, the ghusl is sufficient if she intends to lift only one of them without the other, as the hadath (definition) (ritual impurity) is a single state, even if its causes are multiple. If a woman performs ghusl with the sole intention of removing janabah, it is sufficient and lifts the impurity of menstruation as well. There is no sin upon her for what she prayed during menstruation, believing it to be istihadah (definition) (non-menstrual vaginal bleeding).