Should one repeat the Asr, Maghrib, and Ishaa prayers if impurity is discovered on the clothes after performing them with a single ablution?

If traces of feces appear after the prayer, your prayers are valid, because the impurity is considered to have occurred after the prayers. If you prayed unknowingly of the impurity's presence, your prayer is valid according to the majority of scholars. The trace might be minor and excused by some. You are not required to search for impurity unless you are certain of its existence.