@Pyxis , congrats on getting the first eggs to hatch -- lots of folks don't get that far with their first pea eggs. Sorry about the losses.
It seems pretty unlikely to me that the chicks would die from lack of protein if the lowest percentage component was 18%. They may not grow as fast -- but some people feel that is safer for just that reason, because very rapid growth has been associated with development of leg problems, particularly twisted tibias. Chicks can grow and thrive on 18% so I'm trying to figure out how that level of protein would kill them.
From here (and unfortunately not knowing a lot of specifics), I'm wondering if the chicks didn't pass from coccidia? That's the most common reason for chick losses, and that's about the right age when it starts hitting them. The amount of medication would have been lower with cutting the feed (I've had that happen too
) and even the level of amprolium in the medicated feed is not necessarily enough to prevent coccidia in every chick. Even with medicated feed, coccidia outbreaks can occur, and we know that peachicks are highly susceptible. Those chicks need additional meds and treatment to pull through.
Coccidia can kill a chick very quickly, and sometimes it's not obvious that a chick is sick until it's on the point of death. I'm wondering what you were able to observe last time -- what did the poo look like? What symptoms did the chicks exhibit? Were any of the chicken chicks ill and did any of them die also? Did the peachicks seem stressed at all? Were they warm enough? Were there any issues with them that might have provided clues such as difficult hatching, large red bellies, foot problems, lethargy? Were they eating and drinking well and acting perky? Was there any supplementation, such as vitamins in the water? (Vitamins are great but can affect the amprolium/coccidia.) What kind of cages/brooder/flooring did they have?
I'm also wondering about other possible diseases... I don't know, it just doesn't sound like a nutrition problem to me. Asking lots of questions, because there's lots of experienced folk here who can help. Sure don't want to see you go through this again!