iOS 13.6 Battery Health decreasing drastically

I’m very concerned of my iPhone 11, I got mine from our network provider last October on the day it was released. I have been encountering problems such as my battery health has been depleting and I’m concerned if something might happen to my phone. Every since the software update (iOS 13.6) my iPhone’s battery health has decreased from 96% - 91%. For the past few weeks, my phone’s battery health decreases 1% once a week. I do not know what happened I usually use this phone moderately. I even see to it that do not reach 20%. Everyday I charge my phone 40% and I only charge once a day. I alwaye see to it that I can use the optimized battery charging to that my phone’s battery will not deplete. I usually do not play games and if I do only 2 hrs in one day. What do I need to do?