Blurry Images Help

On my Mac desktop (with no retina) if I open an image url with https it is tiny and if I open it with http it is clear.

With https the image is 24 x 24 pixels (natural size)
With http the image is 320 x 320 pixels (natural size)

From the Media Library the image dimensions are 320 × 320 pixels.

When I open the image url either way on my Macbook Pro (with retina) it works fine with https or http.

I have a SSL certificate on the site.

I have searched forever to find the reason this keeps happening. For those that open the image on the site on a Mac without Retina Display all see the image blurred using https. Can you please tell me how to fix this issue?