I have lost a number of my chickens with what I think is the same disease but different symptoms. One had green poo, one shook her head, one gasp for air, one could not stand, etc. The ONE thing they ALL had in common, (other than the roo I found dead one a.m.) is a slow decline in health. They all get the "I don't feel good" symptom which sometimes develops into other symptoms. This mostly takes a few days to a few weeks before they die despite my stoic efforts to help them. They are 1 black Australorph about a yr. old and 7 J. G.'s (which were supposed to be vac. for Mareks.) Any ideas ? Thanks !!