My chicken have been sneezing (at least thats what I think it is) for couple of months(could be longer but thats when I noticed) Its like shaking their head with a little sound like "took" or you can call it a bark. There is no runny nose, no eye discharge redness etc. All of their weights have been stable or increasing (I weigh them weekly). I am concerned now because from doing this shaking head and barking from once or twice an hr, it has increased to 4-5 times an hr (when I am observing). Someone said there might be worms, but I have not seen any evidence. Winter is fast approaching and they have started a soft molt, so I am trying to be pro-active. Any suggestions?