We hatched a batch of chicks about 6 weeks ago. We kept 2 The one sneezes constantly and its eyes seem puffy. I have not heard the other sneeze but it's been exposed I guess since they live together. The sneezing one eats and drinks well but seems to breathe heavy. I have added probiotics to their water but it did not help. We have never had any respiratory issues in our flock and most certainly don't want any introduced. What could be wrong with it?