Cover block fixed image on ios not displaying correctly

I read that this is an old problem but I have tried dozens of CSS workarounds and none work for me. The issue is that when a cover block is set to fixed that on an ios device the image is megga zoomed in.
Could some one please help me with a CSS that I can drop into my additional css section to only apply to ios.
I don’t need the image to be fixed on an ios I would just settle for it to display as a full image and not zoomed in. But want to keep the cool fixed effect everywhere else.