Hello!
I dont really think that he was poisoned, and here's why!
We once had an infestaion of rats (it was NOT our fault, our neighbor's actually...it is a long story) but we set out rat poison, and the things brought it to our chickens and fed our chickens! They are insanely smart!! Anyways, that silkie roo was dead in a few hours and you could see that he had been bleeding from his vent and mouth and a little from his eyes.
However, if you think that your little guy was poisoned, which he could have been if the dose was VERY small, give him Vitamin K, also found in carrots. This will stop the bleeding.
He may also have Coccidiosis if there is blood in his stool. Try telling the difference in this way: if he is skinny, he likely has just Coccidiosis. If he has been healthy, good-weight, and suddenly has bloody stool, he may have been poisoned. If you really have no idea, take a stool sample and bring it to the vet's. This is only about $10 and it will tell you a lot about your bird's health.
For Coccidiosis, I treat them with 2 tbsp of Sulmet to one gallon.
Let us know how he does!
God bless,
Crystalchik