Sour crop is pretty common in cockatiels, and usually occurs because their crop doesn't empty our completely before you feed them agan. This makes for a perfect environment for bacteria, etc., to breed and make the bird sick.
If you have a regular veterinarian for your birds perhaps he can give you an rx for an antibiotic. I'm certainly no expert, but wonder about the pepto-bismol. Wouldn't there be a possibility of stopping the bird up even more by using that? If you are looking for something to give the bird more sugar in his diet I've always used clear Karo syrup with all kinds of babies and had good luck with that. I think it would be a little easier to digest at this age.
Have you ever tube fed babies? I tried my best to save one from sour crop a couple of years ago by using the tube and getting out all of the crud that was in his crop. Seemed I got a lot out but it was ultimately to no avail. You can also use lactated ringers, saline solution or warm water to fill the crop, rub it gently to loosen the debris, then flush it back out.
How many times a day are you feeding these guys? Watch their crops closely and make sure that they are empty before putting more food down in there. Hopefully if you withhold food for a bit, try to gavage the crop to wash out what is in there and causing problems now, you may be able to save him.
Did the breeder or your vet tell you to give him applesauce? That's one I've never heard of, but different people have different "cures".
Since you have to be away tomorrow, check the bird closely in the a.m. before you leave and instruct your son on how often he should check it to feed it. It will be much better for the bird if he gets hungry than if you fill the crop past what it can hold.
Good luck. This is one of the hardest things to cure in birds, and it seems to affect the 'tiels more than the other breeds. When I first started hand-feeding birds I was told (incorrectly) to give them just as much food as they could possibly hold. And I lost a couple to sour crop.
Let me know what happens!! I'm handfeeding a CAG now and am consistently concerned that something is going to go wrong.
Send me a private email at [email protected]
if you'd like. I'm kinda brain dead right now but will see what comes popping into my head over night.
I really understand how you feel. My prayers go out to this little doughboy.