Why is my iPhone 15 battery capacity dropping so fast?

Hello everyone!

my iPhone 15 started losing battery capacity quickly. The phone was purchased in May 2024. I don't put too much strain on him all the time. Sometimes I play games and hardly use a vpn, I also charge with the original charger. Capacity has been falling rapidly since September. But it's been happening faster in recent months.

December 1 was 96%

December 16 was 95%

January 4 was 94%

January 12 was 93%

January 18 was already 91%

And today is January 30th, 90%

The phone lost 4% of its battery capacity in a month, previously it was not necessary to charge it often, now it has to be done twice a day. The settings show the device usage for an average of 5 hours and 7 minutes.

Please tell me, should I worry about the fact that the battery is defective?

[Re-Titled by Moderator]