OK, just to clarify things - you checked his crop again first thing in the morning? Or later in the day. Checking first thing in the morning (before he gets off his roost, or before offering more food or water after withdrawing last thing at night) will tell you exactly what contents of the crop aren't moving. I'd recommend doing that so you'll know how much crop content does or doesn't get moved. Very important.
Checking even an hour after they wake up gives unclear results.
If you're smelling sour crop, the entire crop must be emptied by your manually. There's a baking soda and water mixture that you can use to do it. Glenda recommends it, and the remaining baking soda in the crop will help to correct the problems. If you do that, don't use ACV on the same day. DO use probiotics starting now and continuing until the bird is well.
You know honestly birds are drinking a lot right now. If you pick them up, they will have water, food, etc in there. Their crops should go down at night and this must be verified first thing in the morning only because they'll hog down more water and food. Crop flushing and treatment is stressful and you don't want to do it unless you're absolutely sure that the bird has crop stasis.
In the mean time, the yogurt will help a healthy bird much less a sick one. The bacteria in yogurt help to give fungi (yeast) competition in the crop. Yeast/fungi without competition bloom and they will cause sour crop. It could be as simple as the stress of heat causing a bird to lose some beneficial bacteria, causing a lack of competition, ending up in a yeast infection and sour crop. So build up the beneficial bacteria again to treat a problem or eliminate a potential further problem if this is a static crop caused by something else.
Would you please let us know how things look doing that overnight fast test? I'm very interesting in being part of the team that helps you help this boy. He sounds like he gets a very good diet and care.
p.s. Animals know it's a holiday!
My gelding kicked the heck out of my mare yesterday and of course I found her after all places were closed. And of course today was the fourth. Thankfully my vet went to the clinic just for her. BUt I'm marking a calendar and putting it in the barn from now on! Every holiday will say "DON'T you DARE get sick!" on it.
