Background Stretching on iOS mobile devices

Hello

I’m having an issue with my background on mobile iOS devices. If the page/post is empty my background is fine. However, if I add anything to the page/post, the background stretches and distorted. I’ve checked other devices, other browsers, as well as troubleshooted plugins and additional CSS. I’ve hit a dead end. Any assistance would be greatly appreciated.

The page I need help with: [log in to see the link]