I lost one hen about 3 weeks ago, now today I have another one sick. Yellow runny poo, she is laying on the coop floor and when I try to make her stand up she is unbalanced. I got the shot for Markes when I bought them as babies in March. All seemed fine yesterday. They are not free ranging. They have sand in there run. There is no blood in poo. I can't find anything that they could have got into and I can't find any sign of worms in poo. Also I put DE all around in coop so it shouldn't be mites. What else can it be?