I'm hoping some of you phone sleuths might be able to help with this mystery please.

My iPhone 13 Mini (bought last August) has experienced a battery drain during the night on three occasions now (over the period of about 6 months). I've woken in the early hours or early morning to find that the phone is dead - before I went to sleep it was at least 90% so I believe it's impossible to completely drain if only on stand by?

Battery health is 100%.

Here's a screenshot of the battery screen. I've highlighted where it started to drain from around 9pm and looked to be dead at around 2am.

What I don't understand is for 'Battery Usage' how the camera app is showing 90%?? No video was recording by the way.

I've never experienced this before with any iPhone - do you guys have any ideas as to what is happening or what I should do? I can take it back to John Lewis as it's well within the 2 year guarantee.