I’m the same issue with a 11 pro my battery lasted all day last week now it doesn’t lates 3 hours all of a sudden and i restarted my phone at 3 percent when it came back on it was at 64% so I’m very confused and my battery health at the beginning of November was at 96% now it’s a 89 percent I got this phone brand new from Apple in June so I’m confused as to how my batter degrade so fast my iPhone 8 Plus has better battery life running the same software iOS 14.2