Need help diagnosing this problem-graphic pic

[Kelly FG]

here's the link for the thread I posted on I & H, but maybe it makes more sense for people here that are good at diagnosing to look at it.
I'm really curious to know what went wrong
Here are my questions-
what day does the chick look like it was at?
why would development just stop under a broody?

https://www.backyardchickens.com/forum/viewtopic.php?id=61595