This my opinion beat feet to the nearest avian veterinarian asap. Have them show you how to properly hand feed this baby. Air in the crop can also mean a yeast infection. Make sure to sanitize sanitize sanitize everything that you are using to feed this chick. That mean washing it well, rinse, then using something like F-10 to sanitize. Never use bleach to sanitize. Personally I prefer single use syringes, use once and throw it away. You are going to need a scale that weighs in mg also. Keep track of the baby's weigh, weigh before you feed every time. I use a notebook to keep track of its weight. A brooder is nice to have but expensive, a make shift one will work. This is what you'll need, heating pad that STAYS on all the time, a five gallon fish tank, towels, paper towels, a digital thermometer that stay in the tank and something to cover the tank.
Put the heating pad under the tank on lowest setting, put a towel between the tank and heating pad. Put the heating pad under half of the tank. Put the thermometer in the tank where you can easily read itand let it warm up. About 85°- 90° no hotter no colder, line the inside with paper towels and rolled hand towel under the paper towels. The rolled towel gives the baby a place rest against. Every time you feed clean the paper towels out, check the poopies to make sure they are consistent with size, no smell, not runny ,not hard either. Any changes to poopies vet time.
@Zara I never feed after midnight and started at 6AM the next day? Does this sound right to you?