Battery Capacity less than 80% is considered worn.That is probably why it drains faster. I don’t know how long you have owned the iphone but the X is 4 ½ yrs old, if the battery is orignal that is a long life. For example, my yr old battery is still at 100% but I am probably a relatively light user. When my iphone showed 80% capacity, it also displayed an advisory in the battery section saying the battery was degraded and needed to be replaced
