My rooster's comb is starting to turn purple in the back. I noticed it this morning during their daily inspection. He was awfully thirsty and it was assumed that he was dehydrated. I have no idea why. There are several waterers in the coop. So I mixed up some electrolytes for him and made sure he had plenty to drink. Then I put some Vet Rx on his comb to increase circulation which seemed to work. And because my flock is incredibly spoiled, I whipped them up some scrambled eggs and added some minced garlic on top. His comb turned red again and all was well. Until this evening... Now the back of his comb is purple again. Not only is his this way, but so is my other rooster's comb. And I heard one of my pullet's sneeze. I'd like to treat my small flock of 8 for a possible respiratory infection and have purchased some Tetracycline Hydrochloride powder, but I am confused as to the dosage. How much of this powder do I mix for 1 gallon?