Warning: Cannot modify header information

I have content experiments set up on one of my pages. It was working fine but now I’m getting a strange error when I visit the page:

Warning: Cannot modify header information – headers already sent by (output started at /home/letsurf/public_html/www.cutaplug.com/wp-content/plugins/google-content-experiments/class-wpe-GCE.php:96) in /home/letsurf/public_html/www.cutaplug.com/wp-includes/pluggable.php on line 876

The page is https://www.cutaplug.com/metal-detecting-secrets

thanks,

Rusty

https://www.ads-software.com/plugins/google-content-experiments/