New PHP, Morning After theme & Woo Commerce

I recently upgraded to the latest PHP version, and after that was unable to access some of my wordpress admin pages (esp the Posts pages), returning a 500 internal server error.

If I uninstall Woo Commerce, it all works. But I’m running the latest version of the plugin, WordPress and the morning after theme, so I’m not sure why that should be a problem.

The error I get says:

“Notice: load_plugin_textdomain was called with an argument that is deprecated since version 2.7 with no alternative available. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2724 Notice: add_custom_background is deprecated since version 3.4! Use add_theme_support( ‘custom-background’, $args ) instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2638 Notice: add_custom_image_header is deprecated since version 3.4! Use add_theme_support( ‘custom-header’, $args ) instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2638 Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2722 Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2722 Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2722 Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2722 Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /content/sites/l/i/litro.co.uk/web/wp-includes/functions.php on line 2722 Fatal error: Out of memory (allocated 33816576) (tried to allocate 35 bytes) in /content/sites/l/i/litro.co.uk/web/wp-includes/cache.php on line 508”

What does this all mean? How should I go about fixing this?