Battery health issue

Hello Apple,

I hope All apple staff are well. I have iPhone 12 pro. It’s battery turned into 88% from 93% within last 10 days. And I didn’t find out the reason. Why is this happening to me? Even it’s warranty period is pending (4 months) There is no as such use of my phone more than attending calls and using social media. Still this is so heart touching to me. I’m so depressed and very disappointed due to this act. I am an old user of apple. I am using iPhone from 5 series and till now. But this time i am helpless what to do with this. Please resolve it’s battery health issue. I shall be very grateful to you.