I brought my iPhone 6s to Apple Store to replace a new battery last year. After several months from the replacement, I found the battery would be draining by 50% overnight. (see the below picture) https://imgur.com/a/f1DLH6W

I tried turning off WIFI and cellular and also turning on Low Power Mode or Airplane Mode. None of them works.

And more strange thing is iOS shows the Battery Health is 100% when coconutBattery indicates the design capacity is only 78%.

Does anyone have the same issue?