I have some baby chicks that are about 2 to 3 weeks old. They have their feathers and are very healthy.
Is it okay to feed them cooked rice and/or cabbage....or other vegetables and fruits at this age?
Many on this forum will say that its OK, and it may be. However, what is best for your birds is to feed them only starter ration until they are closer to the point of lay. Even then, keep it in moderation. If you keep the supplements to under 10% of their intake then you reduce the chances of dietary deficiencies.
Everything in moderation. A tablespoon of rice for an adult is a snack, a table spoon to a chick can be half their day's intake of food. So a few grains here and there for a treat is fine, just don't over do it.