I know this sounds like a stupid question, but my chickens seem to be sick once again. I cleaned out the deep litter after about 3.5 months, put down a light sprinkling of Sevin dust in corners, fresh litter in the coop. In the run (dirt floor) I scoop poo 2 sometimes 3 times a day. Is it possible that they are not building immunities....this is the second time in 4 weeks their poo looks loose, spongie, some copper green in color, and smells quite different than normal. They do not get to free range due to hawks. I have read on other posts that people have been on fixed runs and coops for years with no problems. One person said 30 years for him......what am i doing wrong???