iPhone 4 volume buttons not working

Hi. Just like the title says, the volume buttons don't seem to be working. My phone recognizes they are being pushed, but it does not change the volume of my phone.

Also, the speakers are selectively working. They work on my ringtone and keyboard clicks, but not on Pandora, YouTube, or other social media apps. But they work on headphones.

I've tried resetting and restarting my phone and it's on the latest update. I've also read other threads and can't seem to find a solution. Can anyone help?