Thumbnail quality issue

Hey, we have a website with jetpack enabled. As it is a photography portfolio, image quality is of utmost importance for us. We have the “Speed up images and photos” option disabled, and the full size images load fine, however; the thumbnails are still of bad quality. I’ve tried adding the following codes to functions.php and regenerating thumbnails but it didn’t work:

add_filter( 'wp_editor_set_quality', 'set_editor_image_quality', 10, 2 );

function set_editor_image_quality( $quality, $image_mime_type ) {
	return 100;
}

add_filter( 'jetpack_photon_pre_args', function( $args, $image_url, $scheme ) {
	if ( empty( $args['quality'] ) ) {
		$args['quality'] = 100;
	}

	return $args;
}, 10, 3 );

You can see the difference here:
Original image: https://esraozdogan.gyayingrubu.com/wp-content/uploads/2018/01/ic19.jpg
Bad quality thumbnail: (even the colors are off) https://esraozdogan.gyayingrubu.com/wp-content/uploads/2018/01/ic19-360×360.jpg

Hope you can help me fix it. Thanks in advance.

The page I need help with: [log in to see the link]