Battery Drain

Usually i sleep after i charge my iphone 11, and from 100%, i woke up to 99%-98% after sleeping for 8-10hours. But, this day, i just woke up to 83%! I CHARGED MY IPHONE 11 TO 100% AND DIDN'T USE MY PHONE BEFORE SLEEPING THEN AFTER I WOKE UP, IT'S SO HOT AND WHEN I CHECKED THE BATTERY, IT'S ALREADY 83%!!! This happened twice now so i am so alarmed and anxious about this. My iphone 11 is up to date when it comes to ios udates and as of now, my phone is on ios14.5 and recalibrating it's battery. Though, it happened way back before Apple updting ios to 14.5. I NEED ANSWERS APPLE, THANKS!