Hi nick1,
We have already checked in our theme and there is no any deprecated notice. Might be it is coming from plugins. Once try deactivating all your plugins on dashboard and check whether your problem solves or not.
Also login to ftp and open the config.php file and make your debug mode false. If it is true then make it false.
define( 'WP_DEBUG', true );
replace with
define( 'WP_DEBUG', false );
Thank you!