I'm not sure who the Margaretha you mention is off the top of my head. I haven't dug up my papers yet but I'll try to do that this weekend. It appears that Blattnitz was part of Germany until it became part of the Sudetenland and was then considered part of Czechoslovakia. The Czech version is "Blatnice" I think. The Margaret Plutz in my family was my grandmother who was John Plutz's daughter. She was part of a very large family. 6 or 7 sisters and only one brother, Pete. I don't believe Pete had any children. John's fathers name was also John. Possibly John Paul? I remember grandma Margaret insisting she was of German decent and not liking it if people teased her for being Bohemean or anything else. Maybe that's where the "Czech" comes into the story. I seem to remember Great Grandpa John also having a brother named Matt. I don't remember a Joseph but it's possible. Half the Plutz's had blonde hair & pale blue eyes and the other half were brunettes. My greatgrandfather John Plutz eventually settled in Chicago with his family before 1900. Possibly 1885-1890.
I'll send more when I find my notes. Naturally, anything you have on the Plutz's would be of interest to me as well.