How old are your chicks? Did you get them with the intent to process them for meat?
Because of the genetics, they've been bred for rapid growth for meat production, they tend to have poor organs (sudden death from heart attack is not uncommon), bone issues, and short lives. Some people try to keep them longer, it's necessary to restrict their feed to do that, to try to slow their growth some. They still rarely live terribly long.
https://www.oakhillhomestead.com/2020/06/what-you-need-to-know-about-meat-birds.html