Social Integrations....

Not sure if this is an issue or a bug, but I noticed when you click on a post on my site, every social button that I have selected seems to load just fine except for stumble upon. Stumble upon only loads if I click on load non secure it loads fine. If I don't it shows up looking like the attachment below. (looks like stumble upon icon is missing)

Any suggestions on why the other icons load but not stumble upon??