layout changes with child theme in wordpress

I am using a theme for which I want to create a child theme.

I have noticed that when I switch from parent to child some of the elements in the page slightly - enough to destroy the layout.

I attach an image to show this.

Code below.

How can I stop this 'jumping'

Thanks

here is the child style.css - as you can see its empty really:

@charset "UTF-8";
/*
 Theme Name:   Startuply Child
 Theme URI:    http://ift.tt/1wqYghl
 Description:  Twenty Fifteen Child Theme
 Author:       John Doe
 Author URI:   http://example.com
 Template:     startuply
 Version:      1.0.0
 License:      GNU General Public License v2 or later
 License URI:  http://ift.tt/fSabl7
 Tags:         light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
 Text Domain:  twenty-fifteen-child
*/

I also created functions.php within my child and added:

add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
    wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
    wp_enqueue_style( 'child-style',
        get_stylesheet_directory_uri() . '/style.css',
        array('parent-style')
    );
}