Before the most recent C5 update, my clients website iamfriday.me started not displaying the individual headers we have for each page. When I went to go check on it, I saw there was an update. So I updated and then got this warning:

Warning: Cannot modify header information - headers already sent by (output started at /home/iamfrida/public_html/updates/concrete5.6.0.1/concrete/core/controllers/single_pages/upgrade.php:6) in/home/iamfrida/public_html/updates/concrete5.6.0.1/concrete/core/libraries/view.php on line 899

I'm hoping this points to what is wrong with our headers and how to fix them. But this doesn't mean anything to me. Can someone out there help?

Thanks!
MR