iPhone 8 battery draining

Over the last couple weeks I've noticed my battery seems to be draining faster than it used to. I'm not doing anything different with it than usual. I've looked at the battery health settings and there doesn't seem to be a problem, at least that I can tell. It says my peak capacity is 84%. It was around 89% when I purchased the phone (used) a couple years ago. I have no difficulty charging the battery, it gets up to 100% without any trouble, just doesn't seem to be lasting as long. Any thoughts? Are there settings or apps running in the background that I am not aware of that could be using battery? Or maybe it's just getting time to replace the battery (or the phone)? Thanks.