If she seems ok then I would just watch. If it gets bigger, or she seems to be having trouble breathing, then I would intervene. Hopefully it will be one that resolves on it's own. If she's eating and drinking and pooping, those are all very good signs.
If her abdomen is swollen, that can be an indication of a reproductive problem. If it's fluid, that's ascites, which is from the liver leaking fluid and can be from various illness's including cancers and infections or organ failure. If it's very firm then it could be from infectious material...
Sour crop usually has a smell, as the contents of the crop are fermenting/spoiling if they aren't passing through. If it's that, then crop issues often have another underlying cause, which can take some time to narrow down. I'm going to give a couple of links, faster than trying to go back and...
More information would be helpful. How old is the hen? Do you know when she last laid? Have you seen her droppings and are they normal, pictures can be helpful? Any wounds or injuries anywhere on her, hiding in feathers? Is she thin, or well muscled, is her keel bone prominent? Does her...
Does it feel like air? Baby chicks can injure air sacs fairly easily by getting banged around, running into things, etc. Sometimes those will heal by themselves. If it gets worse, or the chick is having trouble breathing then the air can be released to relieve the pressure, which will also...
I agree with everything @Wyorp Rock has said. I would clean and apply ointment as she described, and monitor daily for signs of infection. If that happened I would start her on an oral antibiotic like amoxicillin (many times antibiotics are not necessary). I wonder if she may have gotten a...
How old is the bird? Hen? Looks like possible rooster damage from him hanging on when he mounts. If you don't have a roo, then watch for a dominant hen doing it, which sometimes happens when there is no roo in the flock.
It can. If the eggs were on the edge of the pile, they may have gotten cooler. Just about anything can happen when they go from blastoderm to fully formed chick in just 21 days. It's pretty miraculous actually. I've hatched in the heat of summer with high humidity (Florida) and that can have...
Sometimes something as simple as temperature fluctuations and humidity can be enough to affect the developing embryo's. Usually there are more issues with incubator hatched eggs, but even a broody can have issues sometimes, particularly if she's sitting on a lot of eggs and they don't get moved...
Glad she's eaten a little on her own. Sometimes supportive care is all you can do. Good luck with her, and hope you eventually get answers to what's really going on.
I generally don't give dairy, too much can cause digestive upset, they don't digest dairy very well. I would concentrate on fluids until she's well hydrated. If she starts feeling better then she'll eat on her own. Tubing fluids can be faster, and generally you get them hydrated first before...
With all the losses, it would be a very good idea to find out for sure what is going on. Maybe Marek's, but other things can often look a lot like Marek's and are not. So it is a really good idea to get confirmation before assuming. Marek's can be manageable, but losses will be higher. But...