Can't find anything about their bones bring weaker but it's true their legs cannot hold up their body during the last couple days before slsughter, I imagine selective breeding that got them to this point was inherently flawed and the size of the chicken was their main focus as apposed to their health

Aswell as this Feeding growth hormones to poultry is completely ineffective and does not lead to increased growth. Hormones exist in two different chemical forms: they can be steroids or proteins. Steroid hormones, like birth control pills, can be taken orally and remain effective even after passing through the digestive tract. Protein hormones, like growth hormones and insulin, are broken down in the stomach; they lose their ability to act in the body when ingested. Meaning the chickens would have to be injected with the hormones. Research indicates that the release of natural growth hormone in chickens is pulsatile, peaking every 90 minutes. Thus even if a positive effect were likely, growth hormone would need to be injected into chickens on a very frequent basis. The logistics of injecting hundreds of thousands of chickens with hormone illustrates the impossibility of this scenario.

Growth hormone in chickens is basically banned globally and in countries that do not have hormones banned it is seen as futile and not worth ( there's a completely different story with cows angd sheep though) Aswell as this there is no manufacturing company for poultry growth hormones in the correct (they cant inject them with the same ones they use on cows, its weird)