Help - Cag Going Light

Hi

Bought 02 breeding pairs in Mar07.
One bird, supposedly a female, is going light.

Rupert was kind enough to supply free Baystril for it.
Condition did not improve after a month.

Vet prescribed Doxicyclin.
Now at end of another month, still no improvement.
Can anyone offer help, please?.

Bought the bird because it could talk and because it has some nice red feathers in its body. However, vet advised that the red feathers are a sign of organ [liver or kidney - can't remember which ] failure.
If vet's advise is correct, dear members, please consider red feather ones as a no-no in your future purchase.

Brgds