Need help with feeding a 3 week old bunny!?

I have a Mama bunny with a litter of 8. They were seperated from each other from about 4-5 days (accidentally of course...long story). All but one are doing great back with Mama! The one though is very weak, very skinny and when it walks, falls over most of the time. The other babies tend to run it over and it won't feed from Mama..I've seperated it from the others for now! I think this must have been the runt to begin with! I have tried to get her to eat from Mama (flipping Mom upside down on my lap) but she wants nothing to do with it. She would rather eat pellets that have been soaked. I did give it some puppy milk replacement the first day...would it be better to continue giving it the puppy milk, soaked pellets or some of each? It will lick off a spoon! It also tried to eat an apple my daughter had..should it eat fruits and veggies at this age? Should I continue to try to get it to eat from Mama each day? If anyone has any advice please get in touch with me asap! Thank you!