iPhone 13 Battery Health rapidly dropping from 100% to 97

I've been using it since the second week of June.

So, you have been using the phone for about 6 months. On average....over time.....the battery is expected to decline about 1% a month. But.....the decline is not linear. Some months it might drop 2% and then not drop at all for the next 2 months. I've seen 3% drops on one of the phones here and then no drop for 2 months after that.

At this point, it would be normal for your battery to be in the 93-94% range.....on average. At 97%, your battery is doing better than average, so you should be very happy.

It is also normal for the battery to decline up to about 1% for every 25 charge cycles. If your battery has completed 210 cycles, then it would be normal to expect the battery to be at about 92%. Again, your battery is doing better than average.

I don't use my messenger but the past few weeks, I've started using it for hours (talking about 8 hours average), and I am wondering if it plays a factor?

That might be a factor if you are using a cellular connection for messaging, since the phone uses up more energy with cellular than regular Wi-Fi.

Bottom line.....the battery is doing very well. There is no need for you to try to babysit the battery or check the settings all the time. It won't help the battery, but it will likely make you more nervous when there is no need to be.

All that you really need to remember is to replace the battery when it drops under 80%. It's that simple.

You are welcome. Good luck!