My neighbor just called me to let me know that 3 of her 5 hens have died in the last two days. She's concerned that they may have something contagious. She says she noticed very dark diarrhea in their coop. Any idea what could be going on, and/or how careful I should be? My chickens free-range. Hers don't, but mine have been known to hang around in the vicinity of her coop. Right now I've got mine in their run. But I wonder how long I have to worry. Thanks in advance for any advice.