iPhone 8 battery isn’t fully charged after being on charger all night?

This is the 3rd morning I’ve notice my battery isn’t fully charged after 9+ hours on the charger overnight. It’s in the 80-90% range each morning. I tried different chargers (all Apple chargers), different outlets and even happened while staying in two different houses so it doesn’t seem to be an outlet, charger or power supply issue. Phone was purchased 2 weeks ago from Apple. Any insight is appreciated!