Keep your column, but wrap each of your text field in the Expanded widget. The reasoning is given from the official docs:
A widget that expands a child of a Row, Column, or Flex so that the
child fills the available space.Using an Expanded widget makes a child of a Row, Column, or Flex
expand to fill the available space along the main axis (e.g.,
horizontally for a Row or vertically for a Column). If multiple
children are expanded, the available space is divided among them
according to the flex factor.
Source: Expanded Class