Hi,
The battery health should not be concerning, over time it will go down as the battery ages, mine lost 10% in the first year of use - and I’m pretty careful with setting up so nothing unnecessary runs in the background.
Now, if your device is losing charge AND charging slowly, it COULD mean the phone is working hard in the background following an update.
There could be a number of reasons. If you’ve updated recently (say in the last 2 or 3 days), it could be that the phone is sorting out some stuff after the update. I’d give it a few days, making sure the device is plugged to charger and connected to WiFi overnight - as it will then finish the background updates by itself when it’s idle and charging.
It could also be that the new iOS created some conflict with pre existing apps. Try resetting network settings on the SETTINGS- GENERAL- RESET option. Also, try a force restart (press quickly an in succession volume up, let go, then volume down, let go, then hold the sleep button for some 20s until your device restarts and you see the Apple logo).
Also make sure all your apps are updated as well.
Another, more drastic measure would be reinstall iOS to eliminate other conflicts that might be hard to spot. PLEASE MAKE SURE YOU HAVE A BACKUP FIRST, then follow these steps to erase and restore your device to a clean iOS install.
Personally, I’ve been having no issues with battery life since updating, but I’ll keep an eye on it.
Hope this helps,
Vicko