Can the baby bunnies eat grass from the ages of 1 to 2 and a half months mine was about 2 and a half and it ate grass and lettuce it died the next day what caused this?

you feed it grass and lettuce please dont do that again i feed my rabbit lettuce at the age of 6-7 monthes. please dont do that agian.I hate it when animals die.it is so sad.Trust me i have had 10 dogs. DONT DO IT AGIAN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!~!!!!!!!!!