Insecure content fix

I am receiving this error with F12
“Mixed Content: The page at ‘https://beautydiet.org/’ was loaded over HTTPS, but requested an insecure image ‘http://beautydiet.org/wp-content/themes/phlox/css/images/pattern/p7.png’. This content should also be served over HTTPS”

How to fix it? Can anybodyhelp. I tried insecure content fix plugin, I am unable to do it.

The page I need help with: [log in to see the link]