After a recent update to the cloudlinux kernel some PHP-FPM services appear to be causing 503 errors on some client websites for the past hour or so. We are working to get this issue resolved asap.
UPDATE: All errors have been temporarily resolved by disabling PHP-FPM and all sites are functioning. We have established a problem with cPanel and their support team will need to correct the issue, there will probably be another series of outages as the cPanel update bug is corrected.