check the crop for impaction..
is it possible she is laying soft shelled eggs?
could the yellow be egg substance?
separate the hen to a safe warm draft free place where you can watch her.
yellow watery droppings can indicate parasites, E-coli, staph or strept infection, among other things.
make up a mix of layer feed, water cooked oatmeal, plain yogurt and cooked chopped egg yolk..make puffy, not soupy...give a couple tablespoons 3 times a day along with regular feed available.
with diarrhea she needs electrolytes..a commercial mix is best, but diluted Pedialyte will do in a pinch.
also..get some Poly-vi-sol liquid baby vitamins, Enfamil brand if possible, no iron..give 3 drops on beak once a day for a week, tapering off for a week.
the best way to know if it's parasites is to have a fecal test done at a vet...just take a fresh sample to be tested..
it would be good and quicker to know what the yellow droppings actually are..especially since she is so weak.
if it's E-coli, or other infection..an antibiotic will be needed..
do you have any antibiotics?
(LA-200, terramycin, Pen-G procaine, Sulmet, Tylan 50, Baytril)
BTW...GREEN in the droppings indicates lack of food.
(undiluted bile)