iPhone 11 Battery Defect or Calibration Issue

Hi,

I am facing an issue with my battery where even after moderate to heavy use the battery percentage remains at the same 70-80% levels (with hardly any drop) and then later on it drops drastically by 50% or so immediately to 20-30% range. However when I plug it back into charge within 30 minutes it had fully charged (not on a fast charger). Today it went from 100% to near 0% and the phone died, when I plugged in for charging within 3 mins it had already reached 35% (not on a fast charger). Some screen shots are attached for reference. Someone please help :(

This has been happening in the last couple of months and even after updating the ios to the latest available version.

My iPhone 11 was purchased less than a year ago and still under warranty until Nov 17, 2020. Currently running software version 13.6.1.

Maya