erinm, so sorry you lost your girl. Below is some info from my chicken handbook that might give you some help diagnosing ~
DROPPINGS (mature birds)
* yellow, watery, foamy diarrhea - colibacillosis (common)
* yellowish or greenish yellow diarrhea - ochratoxicosis (sporadic)
* yellow diarrhea - streptococcosis (not common)
* foamy diarrhea - worms (very common)
I did not include the green-yellow spectrum, but there are several things that can cause that and it sounds like you are into the yellow. I do hope that helps.
I have read that worming meds should be rotated to avoid worms building immunity. In my last worming I used Albendazole (trade name Valbazen), which is one of the broadest-spectrum wormers I know of (it addresses roundworms, flukes, tapeworms). I simply discarded eggs for two weeks afterward. If you (or anyone else out there) decides on the Albendazole, be sure to tell your co-op it is NOT the same as Fenbendazole (another good wormer, not as broad spectrum). Here is the dosage I calculated per Gail Damerow's worming article:
Albendazole 11.35% oral suspension
Chickens (standard) = 4.5 mg/lb.
5 lb hen => .2ml (.19806 ml)
Hope that info helps. Please keep us posted!