Each theme has its own styling for the mendix model, also for data grids and layout grids. Those can differ among them.
Not using a theme is probably the reason for this styling change.
You can look up the theme styling by looking in the project folder (docs-mendix-project folder) to the css/sass <project folder>\theme\styles\css\custom.css or theme\styles\sass\custom.scss
Compare those stylings with your own “no theme styling” (be sure you have set up your own css, like described here:
every theme has its own style,
use the layout grid widget and sort the list on it in order to apply your need.