I had the same problem with one of our babies. If you don't get the crop empty it will die. My husband was over feeding ours. First make sure the food is the right temp. about 105 degrees. Do not over feed. You can find the right amount that your baby should be eating if you go to this site. It will give you the information you need. http://www.cockatiel.org/articles/handfeeding.html
Now very important to get the crop empty. I lost one baby because of this so when it happened to me again I learned how to make a crop bra. This held the crop up so the muscles could empty the crop. This is where I found how to make such bra.http://www.avianweb.com/slowcrop.html
Our Little Darling is still alive and doing well. I did have her wear it till her crop grew to fit her body. If when you take it off and the crop still won't empty put another on.
Good Luck
You can comtact me anytime.
Debbie