How to make form mobile responsive?

I have created a form, but it renders differently on the iphone 5 and 6. On the 6, my users can't see the data that they're entering in text fields.  Is there an easy way to either fix this globally or change the font so that it will work for all devices?

I have checked your above mentioned form http://form.jotform.us/form/51785509965168 and, in order for this to become mobile responsive, you have to set the option from the form builder:

1 - Click on Preference, from the Preferences screen change to Yes on the Responsive Form section, as shown below:

Output iphone 6:

I hope this helps.