Hi Nick,
This one? http://www.gensojapan.org/
Do you have ftp access to your site?
Quick way is to ftp in and rename the plugin folder to plugin1 (or something) which will automatically deactivate the plugins.
You can then install a roll back plugin to roll back to previous versions and reactivate them. Or if you have a quality web host you could restore the last backup. (You are doing backups aren't you?)
That should get you back to the previous working state, from which you can reconsider how you update your site in future. Updating plugins is not always guaranteed to work, especially with old out of date ones, and you need a strategy in place. A staging server is a good one, as you can test updates there easily before applying them to your live site.
One of my hats is a wordpress consultant on https://codeable.io/developers/paul-cohen/