Another poster asked about coughing too. Have you taken any temps?
Mine tend to cough a little when the winter air comes in. The dry, cold wind seems to bring up more dust in the hay at mealtime, and I notice them coughing into it while they eat. Also, many Lamancha owners in upstate NY complain that the breed is not well suited to the cold and they tend to have sniffles and wheezing all winter, despite pneumonia vacs and antibiotics.
I don't personally have experience with lungworms, but have you considered that, and given a good wormer for that specific worm?