Since you have had this sort of thing happening in your flock for a month or so and lost a couple of birds, I would have the next one necropsied if you lose any more. This is obviously a respiratory infection going through the flock. CRD/mycoplasma may be the cause. Tylan is good, but there is one drug called Denagard that is supposed to be better for treating CRD and is only available online from QC Supply. It is more expensive and very bitter tasting, but apparently has no resistance built up to it like some other drugs. Here is a link to finding your local state vet for questions about disease, and also to talk about necropsy information. When this keeps happening, you need to figure out what organism you are dealing with.
