Custom font not working in Firefox beyond home page

I am trying to use two custom fonts on my blog: one for the post and menu titles (Brandon Grotesque) and one for the body text (Proxima Nova).

On Chrome, both fonts work on all pages. Yay!

On Safari on my desktop, both fonts work on all pages as well.

But on Safari on iPhone/iPad, and on Firefox (and I assume IE as well, though I haven’t been able to verify yet), the custom font for my post and menu titles works only on the homepage — not on any other pages. Yet the custom font for the body text works on all pages.

Does anyone have an idea how I might be able to fix this? Thanks so much!

http://emilymccall.com