Hi Kyle,
Thanks for your reply. I am using those shortcodes, and they do not work for the iPhone 6. I thought they would work, but where content shows up for the iPhone 4 and 5, nothing but white space shows up on the iPhone 6 in portrait (visible-xs), or in landscape (visible-sm).
I believe this can be fixed with a css hack.
(css) device-width of iPhone 6 is 375px, of iPhone 6 Plus is 414px. Note that iPhone 6 report report window.devicePixelRatio = 2 while the 6 Plus report window.devicePixelRatio = 3 (while not truly at 3 DPR)
See this link for a reference:
http://mydevice.io/devices/
What do you suggest?