Rabbit sudden death 3 weeks

Question
I raise rabbits for a local pet store and have never lost any once weaned.Today I had 2 die without a mark on them.There is a older litter in the same pen that seemed to
get along with the new litter Neither rabbit was malnourished or thirsty as I always watched to make sure they get to water and food.I have never seen any sign of the older siblings attacking the in any way.

Answer
A lot of things can cause sudden death, especially in young rabbits. Without a necropsy, there is no way to be sure of what it was. It could have been any number of digestive problems. It could have been what breeders call "faders" which are just kits that fail to trive. It could have been a lot of things.