Infectious bronchitis virus, one of the handful of respiratory diseases can cause reproductive problems in hens, especially when they are infected at a young age. It can cause sneezing every few minutes, clear thin nasal drainage, and congestion. Wrinkled or corregated egg shells is a sign. My flock was affected with this, possibly from wild birds in the area, and it tends to spread through the whole flock over weeks to months. Survivors are carriers for 5 months up to a year after, so it is best to not hatch or add new birds for a year after the last chicken has symptoms. Otherwise, it keeps spreading. There is no treatment, but IB symptoms last about a month. It is much more severe in young chicks in the first few months of age.