I've just run into an annoying bug regarding custom embedded fonts in an iOS app. It turns out that if you're embedding multiple fonts from the same family, the compiled app will for some of the fonts use one of its siblings instead.

This answer on the invaluable Stack Overflow tells you to change the family name in each of font files to get around this issue. Here's one way of doing that:

1. Download and install TTX/FontTools.
2. Use the newly installed "ttx" command line tool to create a .ttx file from each of your fonts files.
3. Open these .ttx files in a text editor and use search and replace to rename all instance of only the family name. I replaced them with the name of the particular font I was modifying (eg. "MyFont" became "MyFontBold").
4. Use "ttx" again to convert the edited .ttx files into .otf files, ready to be added to your Xcode project.