I do not know since when, but it is recent, my site has a bad score with GTmetrix. The problem is loading full size images instead of thumbnails, in “blog” mode from the list of articles.
You can try with GTmetrix with my home page: https://willyblanchard.ch/ (I don’t know where to link an image), The score is zero for image optimization. I have noticed in recent days a decrease in visitors.
(Sorry for my english)
Thank you !