Why is there no sound in games but other apps are okay?

I have no sound in my game apps (plants vs zombies, minion rush, etc.) without headphones, but all my other apps are fine (duolingo, audio book apps, etc.), i.e. They have perfect sound in my game apps without headphones. So it seems to not be a hardware problem.

I've followed all the steps in the troubleshooting sound article (tried soft reboots, cleaning, bluetooth off, headphones in or out, etc.), and still no sound in games. Super frustrating since that's why I have the iPad in the first place: it's a gaming tablet for my family.

I appreciate all help. Thank you!