Suddenly Podcast app only produces sound through speaker, not headphones

I have not updated to iOS 8 on my iPhone 4S because I heard there were issues, and I've already ordered (but haven't yet received) my new iPhone 6. I don't know if there was a Podcast update that downloaded automatically separately, but suddenly last night, I couldn't hear any sound from the Podcast app through my headphones. I thought it might be a problem with the headphones, because when I removed them, the file played fine through the 4S's speaker, and when I attached it to a clock radio later last night, it played fine through that too.

This morning, however, I tried listening to songs via Spotify with the headphones, and they worked just fine. But the Podcast app still didn't produce any sound. OR, rather, when I turned the volume to max, you could hear something, but not loud enough to actually make out the voices. I then tried playing an album in my Music app, and it worked fine. I tried restarting the iPhone. I tried deleting and reinstalling the Podcast app. I tried a hard reset of the iPhone. The only result from all of that was that now something's wrong with the Music app too, and while the music track comes through, the vocal track is very quiet, almost inaudible.

Anyone have any idea what's going on, how/why this is happening and most importantly, what to do about it?

Help!

Aaron