Children of Flem Mcdowell and Sarah Caldwell

Looking for information on the following children ONLY:

Martha McDowell born about 1897 and her siter Fannie McDowell born about 1904 to Flem McDowell and Sarah Caldwell. Martha was in the 1900-1920 census for Pike County, GA - living with her parents. She was not in the 1930 census for Pike County. Fannie was in the 1910 census for Pike County - living with her parents. She was not in the 1920 and 1930 census.