The phone has 40-70% when I go to sleep and lost almost or all that by morning. I have tried the usual tips to turn off location etc but no difference. Diagnostics to Apple turned off. My GFs 7 has started doing the same. Battery health says ok 85% on mine. Edit - 11.4.1 just appeared and installed. It doesn’t mention fixing this but who knows. My GF installed it when it appeared on her phone yesterday too so maybe that will help.