Chickens molt around 16-18 months old and then yearly thereafter for the mist part. In some chickens you may not notice a molt except for the loss of tail feathers, while others look featherless in large patches. They will usually stop laying while molting. Every chicken will molt at different...
Welcome to BYC. How old is your hen? Has she molted this year? When there is feather loss from feather picking or rooster damage, feathers may not grow back in until the next big molt.