It's not unusual for young chickens to have full crops as they are in a rapid growth stage and eat almost continuously. I would not be concerned unless the crop feels hard which probably indicates that it is impacted. An impacted crop can be caused by eating rough vegetation while free ranging or over dosing on grass or fiberous matter. In extreme cases, it can close off the bird's windpipe and suffocate it. Most people try to treat the impacted crop with a combination of oil and massage but it may be necessary to open the crop to remove the material. That said, impacted crops are uncommon. It's more likely that the bird is just eating a lot.
