Sadly mine went the same way immediately after updating to iOS 13, and I have read the same thing in this and other forums. The common belief on the internet is there is a problem with iOS 13, but Apple have not admitted this, and the usual advice from this forum and Apple is you have a bad battery and should replace it, and/or turn off a lot of stuff.
The coincidence is far too great that so many batteries, many, like mine, inside the 80% upwards of battery health, should suddenly suffer such a sudden heavy drop in battery life, and Apple's stance has resulted in lost credibility as a result. Strange thing is, not all phones are affected, and I have tried many ways to restore and update mine in case the method of updating is the problem, but the improvement I managed to gain was not great.