We have six girls and they are different ages. Our oldest is 4 1/2years old (Trouble); the name says it all and she is top hen. The next three (Lacey, Lucy &Lucky) are 2-1/2 and the next two (Betty & Beauty) are one. All are different breeds and all are molting except Trouble. No one has bad plucking behaviors. What could make them molt? Our girls free range and are all on feather fix, now. We supplement with mealworms, fresh cucumbers and other goodies such as collard greens. We have 15sq coop and a mini coop which is sixsq. We keep pine shavings on the floor and change them everey 2-3 as needed. We have also keep diatomaceous earth in our nesting boxes. We have had no egg production and as I stated 5 are molting. Plus our weather has been down to the 30’s - cold weather and half naked chickens makes me worry. Thoughts?