サイトが全てログイン出来なくなりました。

ご教授いただけないでしょうか。
ブログを3つほど運営しておりますか、突然全てのサイトにエラーが出てログイン出来なくなりました。
色々と調べて見ましたがお手上げ、、なぜ全てのサイトが一気に同じ状況になったのか検討もつきません。

エラーメッセージは以下のとおりです。教えていただけると幸いです。
何卒よろしくお願いいたします。

Fatal error: Uncaught Error: Call to undefined function wp_fix_server_vars() in /home/redays/re-1day.com/public_html/wp-settings.php:76 Stack trace: #0 /home/redays/re-1day.com/public_html/wp-config.php(94): require_once() #1 /home/redays/re-1day.com/public_html/wp-load.php(37): require_once('/home/redays/re...') #2 /home/redays/re-1day.com/public_html/wp-admin/admin.php(34): require_once('/home/redays/re...') #3 /home/redays/re-1day.com/public_html/wp-admin/index.php(10): require_once('/home/redays/re...') #4 {main} thrown in /home/redays/re-1day.com/public_html/wp-settings.php on line 76

Fatal error: Uncaught Error: Call to undefined function wp_get_server_protocol() in /home/redays/re-1day.com/public_html/wp-includes/functions.php:1412 Stack trace: #0 /home/redays/re-1day.com/public_html/wp-includes/functions.php(3474): status_header(500) #1 /home/redays/re-1day.com/public_html/wp-includes/functions.php(3421): _default_wp_die_handler('<div class="wp-...', 'WordPress &rsaq...', Array) #2 /home/redays/re-1day.com/public_html/wp-includes/class-wp-fatal-error-handler.php(233): wp_die(Object(WP_Error), '', Array) #3 /home/redays/re-1day.com/public_html/wp-includes/class-wp-fatal-error-handler.php(152): WP_Fatal_Error_Handler->display_default_error_template(Array, false) #4 /home/redays/re-1day.com/public_html/wp-includes/class-wp-fatal-error-handler.php(57): WP_Fatal_Error_Handler->display_error_template(Array, false) #5 [internal function]: WP_Fatal_Error_Handler->handle() #6 {main} thrown in /home/redays/re-1day.com/public_html/wp-includes/functions.php on line 1412