Well for pigeons you always have to make sure there fed right when the crop is completly empty, pigeons are fed parrot formulas as baby squabs too so hopefuly my skills can help.

I would just keep feeding the baby after it's crop empties, make sure the bird is getting more food inside it's tummy then from spilling, is it pooping more? & when you feed it after the crop is empty does it churp for more when you bring out more food? never feed a baby bird food if it's not reacting towards the food.

I hand fed my morning doves but I did not use a tube I used a little plastic cup then put some material on the top then cut out a tiny hole for the baby doves beaks to go threw I heard this way is more simple and there is a less chance of the baby drowning from the tube feeding, remember if the crop looks empty feel it just to make sure because sometimes it's the position the way the bird is sitting.

I would go to some pro parrot sites to ask for questions.