I think that Krotoschin was the area of Posen that contained Koschmin, Germany now Kozmin, Poland.
Were these Tuchs connected to the Tuch family in Koschminn/ Kozmin? The names I know are brothers: Isidor Tuch, Hermann Tuch and Aron Tuch. Their parents were Josef Tuch and Dorothea Tuch nee Schulmeister. The men would have been Cohenim.
Other Tuch family members from the Koschminn/ Kozmin area were Raphael Tuch born 1821 Koschminn and his father Elias Tuch.