I have a hen that has had bright green runny poo for a few days, and is now very lethargic. Went to let them out of coop this morning and discovered another hen starting with the same runny green poo. I have given ACV, probiotics, and vitamin boost. The only thing that has changed was a new bag of feed ( same brand, but they have never been a fan of). I have ordered a new brand of feed, to arrive soon. What could be going on and how should I treat?