It's been a while since I've made a post...
You could ask your vet to do a fecal float on some collected fresh droppings to look for coccidia and worms. You also may want to purchase a brand name layer feed in case that is the problem. Also look for regular droppings, since cecal droppings can be yellow and runny. A cecal dropping occurs after about every so often, and they tend to look shiny like caramel or chocolate syrup (sorry for the comparison.) Here is a good article with pictures of normal and abnormal droppings: http://www.the-chicken-chick.com/2012/02/whats-scoop-on-chicken-poop-digestive.html
- Master Tuber
But I have nowhere else to turn for help with my situation. I recently had an issue with the neighbors dog (from about 5 acres away...) and lost a number of hens and my rooster. I went out and purchased 3 four month old hens and made a separate area in my current run for them. They are treated for numerous diseases by the breeder and show now sign of illness other than two have yellow diahrrea. It's been several weeks and they've been given probiotic immune boost treatments, but their poo is still the same. They are active, eating, drinking, show no sign of illness, and there is no sign of disease spreading among the rest of the flock. I suspect maybe their current feed being layer pellets and a different brand might have something to do with it, but after 3 weeks and absolutely no change, I think it could be another issue. Any ideas? Again, no sign of illness or spread of disease. No bloody poop either, just yellow and mostly runny.
Can you post a picture of the yellow poop?