My header image on my website (dorinart.com) is perfectly positioned in all browsers including android mobile browsers but when I open it on IOS (iphone, ipad) it only shows the top right corner of the image (you can check if you open dorinart.com). How could I resolve this issue?

my css looks like this:

```
.header{
    background: url('../img/banner5.jpg');
    background-repeat: no-repeat;
    position: fixed;
    background-size: cover;
    min-height: 730px;
    position: relative;
}

```