I have 8 Rhode Island Reds that are about 5 months old. I'm worried about one of them. Her comb is turning black and it appears to be reducing in size. Is she sick? Do I need to do anything for her or the other birds? I believe she is laying eggs because they are laying about 8 each day. The only other possible issue is on occasion I see some black tar like poop. It is sticky, stinky, and hardens like plastic. I have seen this for several months so I don't think it is related. They are free range in my back yard of about 1/2 an acre. They have access to oyster shell. Their water is fresh because I use poultry nipples on a 5gal bucket. I feed them Nutrena country feeds 16% layer crumbles. I just recently started to give them a small amount of oats and corn. I have put down diatomaceous earth in their dirt baths a couple of times (the last was a couple of months ago). I have given them fresh habanero and garlic as de-warmer/preventer a couple of months ago. Thanks in advance for your help. Sorry for the long post. I just wanted to be thorough and answer any possible questions.