Feeding the mash is fine.I don't have access to a vet that will treat or test poultry but I do have baytril left over so I'll try that. I'm pretty sure it's not worms. They don't free range (unless you consider the chicken tractor occasionally) and no others are sick. I have valbazen in my chicken emergency kit but I'm hesitant to make her even sicker considering she's so lethargic.
I've been giving calcium but haven't seen any improvement. I can't get her to eat solid pellets. Only a little bit of mash.
If you have Baytril, then try that. Not sure what else you can do unfortunately.
It really stinks.