You can check the battery health under settings -> battery -> battery health & charging. If the battery capacity is between 80% - 90% that's absolutely normal and it could indicate that there are some settings or apps that are draining your battery, i.e. a rouge app that's doing something in the background or Apple's frequent locations setting is on.
You can check the former in the same batter settings and the latter in settings -> privacy & security -> location services -> system services.
Batteries are considered consumables and deteriorate over time. Usually, you can expect the battery capacity to drop around 10% each year.
If the battery is much less than that it may be faulty. Apple runs recall programs on a variety of parts/products so it's worth checking it as well.
The best starting point would be to contact Apple Support and see what they say.
