Been over two weeks since I lost a 7 month old pullet. It was random, unexpected, and didnt notice any signs. She was weak and not eating in the morning, by 6 she was dead. So of course you become extremely aware after that trying to figure out something. I have had a few runny stools from a couple chickens. And I have noticed a couple black spots on my Roosters comb. One other hen has a spot on hers. There is no puss, no difficulty breathing, great appetite, but overall egg production maybe only slightly down. I have attached a couple pictures, two of the roosters comb (see the spots, and then its almost white flakes, dry skin like?) I also attached an image of the stool. THey arent all like this, but some are, green and runny.  What ever it is, do I vaccinate (too late isnt it?) or treat with antibiotics? I have a total of 16 chickens.