I have a coop with 17 chickens. Some are about 3 years old, some around 2 and others about 6 months old. They have been one by one getting sick. I have put up tin all around the base of their run so they are contained and do not spread anything. Also being very careful going in and out to not spread anything to anyone else. Today I noticed some of their eyes are bubbling. The sickness seems to only be affecting my older hens. So far the symptoms are sneezing, sort of coughing, rattling breathing at night, and now the bubbling eyes. No lethargy and they are all eating and drinking like normal. I have been giving them nurtidrench on their food, poultry booster and vet rx in the water and even making them special food to boost their immune systems. I'm looking into getting them tested for Mycoplasma gallisepticum but I live in a very rural area so any advice is welcome on how to help them and make them more comfortable.