Can someone tell me if my rabbit is old enough for veggies?

It is very important that vegetables and other types of fresh food are introduced
slowly and carefully. It is often best to introduce just one kind at a time. Don’t be
tempted to give your rabbit large amounts in the beginning. This can cause soft
stools, diarrhoea or stasis. Start with one vegetable (e.g. celery). Offer a small
piece and wait for at least 24 hours. If there are no soft stools, a larger piece can
be offered the next day. If the droppings get soft, discontinue the introduction,
and try again some other time. Take your time, and allow 5-7 days to introduce
each vegetable.
The digestive tract of young rabbits is not fully developed and they may suffer
diarrhea if the diet is changed. Watery stools are, however, more often the result
of an infestation of the digestive tract by coccidia, a major cause of death at this
young age. Young rabbits will start to nibble on hay and fresh vegetables after
leaving the nest, at age of 2 or 3 weeks. If the young does not suffer adverse
effects, this natural behavior should be encouraged, so to help develop a healthy
bacterial flora in the intestine. If a young rabbit does not handle fresh food well, it
should be stopped during a few days, and then reintroduced slowly. Other causes
like parasitic infestation or environmental conditions should be ruled out