Fixing insecure jpgs to get SSL padlock

I just purchased an SSL certificate for my website. It’s been installed, but https://www.whynopadlock.com/ shows that I have 26 insecure items (all jpgs), so I don’t get the padlock. How do I secure those?

And, almost every photo was uploaded to the site the same way, via upload in WordPress’s CMS. So I don’t experience this problem again, any idea what caused these JPGs to be insecure but not others?

Also, https://www.whynopadlock.com/ says that I have an” Insecure <form> call.
Found on line # 359 in file: https://www.louisvillederbyhomerental.com/index.html&#8221; (it’s to subscribe to my TinyLetter newsletter). Is it possible for me to secure that form call?

Thanks!