Hi antdude,
Typically, "A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions." As the battery is on and nearing depletion it's likely the reason your apps aren't updating automatically.
You can view the details regarding your battery health here: iPhone Battery and Performance - Apple Support
Additionally, with app updates there are additional settings to check. The "ask if over 200MB option" when using cellular data is one. The article here in the section quoted below has a great visual.
"How to turn on or turn off automatic updates on your iPhone or iPad
- Go to Settings.
- Tap App Store.
- Turn on or turn off App Updates.
"
If you continue to have issues or want to go over your options for service regarding your iPhone battery, reach out to Apple Support directly. The links below will get you started.
Contact - Official Apple Support
iPhone Battery Replacement - Official Apple Support
Contact Apple for support and service - Apple Support
Cheers!