Is the chick 4 1/2 weeks, not months right? I would be a little concerned that she could have coccidiosis. Some chickens can have slow crops with coccidiosis. But I would watch for both a crop disorder and cocci. Corid is the treatment, and most use the maximum dosage of 2 tsp of the liquid or 1.5 tsp of the powder per gallon of water for 5-7 days. Once Corid is started, if you do treat with it, stop any vitamins until after treatment. You can give a couple of drops of the undiluted Corid as well, twice a day as a quick boost.
@azygous is very good with crop problems, so I hope that the chick gets better soon.