iPhone 12 battery draining

My iPhone 12 was purchased 2 years ago (June 2022) and the battery health says 87%. A couple of days ago the battery started acting up. It charges slowly and then dies slowly. It lost 7 percent in 20 minutes, so averaging about 1 percent loss every 3 minutes, and during that time all apps were closed and I only looked at the screen maybe once. Here’s what I’ve tried and what hasn’t helped:

-Thoroughly cleaning out the charging port (because I initially thought it was an issue with the port, but since it won’t hold a charge it’s clearly not that).

-Turning off background app refresh for all unnecessary apps

-Turning off Optimized Battery Charging and Clean Energy Charging

-Updating the software

-Turning off Bluetooth

-Taking it out of the case because it felt kind of warm

Does anyone know why the battery health is 87 percent but it’s draining battery so fast all of a sudden? The screen has one small crack so could it be that some liquid got in there and that’s what is making it act up?

Update: The battery health screen now says, “Charging was on hold due to iPhone temperature.” Is this a sign my phone is on its last leg? It’s been acting this way for two days but now it’s out of the case and a little better. The case isn’t new, I’ve had it on for months and never had an issue.