All content is HTTPS, but browsers warn of HTTP mixed content [closed]

You have “www.wisconsinwetlands.org” URLs redirecting to insecure “http://wisconsinwetlands.org“.

The cases you have used these is in the images on the page. Every image that is set as “https://www.” redirects to the insecure version.

So while you do need to fix that and correctly configure your setup so that both “www” and non-www URLs are secure, you could quickly solve the problem by removing the www from your image URLs.