I'm having a problem with images I use as paralax background fill... they look perfect in a desktop/laptop pc/mac but in ipad an iphone the same images look like they've been zoomed in a zillion percent. I haven't designed the breakpoints yet, but I don't think that has anything to do with this issue...
One other thing, the first image in the site is a background fill image but it rolls up with the site (no paralax fixed effect) and it works correctly...
It's very likely there is a stray element off the page somewhere that's causing the backgound to expand. Without a link to the site, or seeing a copy of your .muse file, it's very difficult to know for certain.
Do not use parallax and fixed background - this is the reason, especially this is critical for Apple.
Isn`t parallax for mobile not recommended anyway?
This would mean, you have to set breakpoints for mobile (768 and smaller) and replace your parallax with something less playful.