I understand. My dog got into a neighbor's rat poison so I think you will have better results calling the company that makes the poison. They will be able to tell you if what you're experiencing is from the poison or not.
From what I know of rat poison it causes animals to bleed to death internally. I would find out from the neighbor what brand they use then call the helpline on the packaging and ask them. They're usually very helpful. Then lock your chickens in the run until you sort things out