According to Isabella and Ferdinand what actions did wicked Christians take that must be stopped

Their interactions with the Jews

Explanation:

According to the  Edict of the Expulsion of the Jews (1492), it was discovered that some "wicked" christians were having interactions and dealings with the Jews. These interactions were said to have eroded into the Catholic faith. Therefore, the King and Queen issued the Edict in order to stop those christians and also purge the land. The Edict authorized all Jews and non-Christians to leave the land.

Ferdinand and Isabella were known as the Catholic Monarchs. They were said to be second cousins and were both from the House of Trastámara and both descended from John I of Castile.  The unification of Spain can essentially be traced back to the marriage of Ferdinand and Isabella. This is generally accepted by all.

most camps were located in the area of the general government in occupied poland