I'm sorry to hear about your hen
I don't think you are doing anything wrong. Sadly, this is very common in laying hens. I hate to say - this is just the way it is, but frustratingly that seems to be the case.
It's not uncommon to lose a couple of hens within a short period of time to something like reproductive disorders and then you do wonder if there's anything you can do, you doubt yourself and begin to think you could have prevented it somehow. I've been in your shoes (many others have been too) and from everything I can read, study, research - there is not much that can be done. Sometimes having "better quality" stock (non-hatchery)
might help, but that takes time (years) to find out if the outcome will be different.
You have received good suggestions and links from the others. You might find the video in the first post of this thread helpful as well.
https://www.backyardchickens.com/th...ions-my-youtube-video-graphic-photos.1201052/