They are supposed to be given grit. But I suppose that’s not the issue since you said they all have access to the gravel. Is their floor too slippery? They don’t have good grip on flat surfaces. If you’re scrapping it clean and they can’t grip on to anything maybe they can’t keep their legs...
You said that one flock is on gravel. Do they both have access to gravel? Are the dying ones getting any grit in their diet? So sorry they are dying. That’s so frustrating.
