Thank you for your help and suggestion. I’ve already tried your method. I’ll wait to see if any improvements come.
I also did settings reset.... by doing “Reset All Settings”.
I did it for three devices together as they all are on the same Apple ID.
I do see some minor improvements. Like instead of getting to see 65 percent battery In the morning after switching my phone off (switched off fully by slider) at night with full 100 percent charge, today morning the charge left was 72 percent.
My iPhone 7 loses battery loses battery at a consistent pace... whether switched off or on.... and it’s slightly warm (Not really hot as reported by many of the members here) almost all the time. Slightly warm at upper right corner. If this information is useful to make any diagnosis.