iPhone 15 Battery Health Drops

Hi all.

Hope there is anyone who can give me a information or answer my question.

I bought my iPhone 15 (early December) and I checked my battery health (as today) it shows 97%.

Drops 3% just in one month is unexpected issue and I really confused.

I use original accessories. Always charge regularly. For a device's prices that are not cheap, Apple is very disappointing. It seems that currently the company more concerned with upsell stocks in the market than quality.

Does anyone experience the same thing? Or any tips?

Your answers is highly appreciated!