Slide In share icons give Mixed content warning over https

Hi,
I have a multi-site installation and have it served over https. But if I add the Facebook, Twitter or LinkedIn social share to the Slide-in, I get the warning "Mixed Content: The page at 'https://subdomain.mydomain.com/' was loaded over HTTPS, but requested an insecure script 'http://platform.linkedin.com/in.js'. This request has been blocked; the content must be served over HTTPS". The Google+ icon does not have the same problem and loads over https.
Everything else on my sites load over https too.