Spotify's Volume is Too Low on Android; all other music apps are fine.

[chrmicklus]

I've been having a problem recently with Spotify's output volume being too low. Here's what I've done so far.

Cleared Android's cache partition.
Uninstalled/reinstalled the Spotify App.
Performed a factory reset of my device.

My current Android version is 6.0.1 on a ZTE Z958 (ZMAX 2) through AT&T. I also have a Spotify Premium account.

All other apps (YouTube, Soundcloud, Android's default music player, etc) play at their regular volume, but Spotify's output is much lower.

I'm hoping there's something I missed. I love Spotify but switching to another service seems more appealing than buying a bigger sound system.

Thanks for any help!