Given the timing of how this happened, there’s no other possibility but your plugin.
I created the page 2 weeks ago for a client, last week got the client’s feedback and throughout all that time, all images were working perfectly.
Then yesterday, as part of final edits and optimization of the page, I turn on EWWW, turn on lazy load, and run the image optimization tool, and once that tool had finished optimizing the images, suddenly half of them are not displaying properly, and I can remove the image and re-add it but it still won’t display if id didn’t before. As I’m building this page on Divi, it should be automatically applying the HTTPS protocol and if it was not, I’d be seeing signs of this issue on other client’s sites I’m running on Divi, and this issue would have shown up well before this, not wait until the specific moment when your image optimization algorithm had finished running.
If some images are in fact getting their src values replaced with “http” instead of “https” like it should be, it has to be your plugin making those changes.
When I deleted one of the problem images, permanently from the server and re-uploaded a clean copy, the image worked normally again. So reverting to an image untouched by your plugin fixes the issue. I am noticing the images display normally in the Divi editor, so that would indicate the image files themselves are not being corrupted, but the URLs of the optimized images are apparently being replaced with the wrong protocol, and removing and reinserting the same image does not seem to fix this, so it’s obviously happening behind the scenes, among data I normally don’t have access to within the WordPress Admin panel.