Sevin is very toxic, so what I (should) do is wear long sleeves, a mask, disposable gloves, and take a shower afterwards.
I put mine in an old sock (you can use old stockings too), tie the top in a loose knot, and shake it under the wings, near the vent, and basically powder puff the whole...
http://chat.allotment.org.uk/index.php?topic=17568.0
the "poo page" for you to diagnose poo
http://www.attra.org/attra-pub/coccidiosis.html
coccidiosis page since Blackbird12 mentioned it, although it is usually in younger chicks unless there is immunosuppression...
Are your chickens shaking their heads about every 5-15 seconds, as if to shake off something on their necks?
If so, then it could be mites. Please note that when my chickens had the Northern Fowl mite, they were shaking their heads as I described, and I could never find one on the chickens. I...