I had 12 chicks that are about 8 weeks old. They are in the house in a pallet sized box. This is our second year with chickens. Our older flock is all outside in a big coop and we let them out to free range. We took the young ones outside twice so far since we had nice days. One chicken started acting sick, lethargic standing still hunched over with her head tucked in and Feathers puffed out and eventually stopped eating and passed away. A second chicken assumed the same posture and we had already isolated those two, they would stand close together huddled as if chilled. The second victim seems to still be eating and drinking. Now a third hen has assumed the posture and is having trouble standing up. Corid arrived at the house yesterday and I added it to their water. Previously, I was giving electrolytes with a probiotic and I also had a bit of a powder to mix with water that had an antibiotic in it that a local Feed Store gives to their new chicks. Should I try injectable Tylan?