I would at least get her company she can see, you can keep them apart in the run, but a bird should really never be alone. I can't stress that enough.
It's very difficult to make a diagnosis online, especially with these very common symptoms, only a vet can make a correct diagnosis. Could you...
No there is not always blood.
The sporozoites and merozoites attack the surface cells of the intestines. After replication, these cells burst and render much of the guts unusable, that's why you get diarrhea. The blood vessels are not laying directly in the intestines but some layers above the...