I've never wormed my chickens, I haven't seen any sign of worms. No weight loss on the girls, picked one up the other day felt heavy and solid. How often should they be wormed? They were about 4 months old in Apr.. How old are they when they molt? Mine still have a full body of feathers. They do like the spot lights shining on their run and coop. So they are getting about 14 hours a day of light.