iPhone 6 Flexbox Wrapping Issue
The core of the issue was persistent in iPhone 5 and 6 through all browsers. In the end it had to do with setting a percentage width. Once I removed that everything stacked as it should. I wanna thank /u/andrei-gheorghiu as his JSFiddles ( in a deleted answer ) pointed me in the right direction.
#flex {
display: -webkit-box;
display: -webkit-flex;
display: -ms-flexbox;
display: flex;
-webkit-box-orient: horizontal;
-webkit-box-direction: normal;
-webkit-flex-direction: row;
-ms-flex-direction: row;
flex-direction: row;
-webkit-flex-wrap: wrap;
-ms-flex-wrap: wrap;
flex-wrap: wrap;
}
#flex .item {min-width: 200px; min-height: 300px;}
#flex .one {background: blue;}
#flex .two {background: green;}
#flex .three {background: red;}<div id="flex">
<div class="item one"></div>
<div class="item two"></div>
<div class="item three"></div>
</div>