This is my first post here and this is my first year of raising chickens. I have 4 chickens and currently they are about 15 weeks old. In the past week or so i have noticed that there is a lot of feathers on the floor in my coop. Also 3 of my chickens have bald spots behind and bellow their ears and one of them even has a little reddness. I have also noticed that their combs seem pale and chalky. Is this caused by mites and what should i do to get rid of them if my chickens have them?