Must I repeat my Maghrib and Isha prayers if there were traces of feces on the prayer spot after the two prayers, knowing that my clothes were not affected?

Doubt about the presence of stool before or after prayer does not invalidate the prayer, for the default assumption is that it occurred after the prayer. If a woman is certain that stool was present before prayer and she prayed, unaware of its presence, her prayer is also valid according to the preponderant opinion. Therefore, the Maghrib and 'Isha prayers are valid, and there is no need to make them up. Doubt about the expulsion of some stool before prayer does not affect the validity of the prayer, and there is no need to verify its expulsion, because the default state is purity until the presence of impurity is definitively established.