I know being puffed up is a sign of cocci. Not sure about the other symptoms.
Bloody stool, but not always. And listlessness. Maybe reduced feeding and drinking. Are you using medicated starter? Do you have other chicks? Are you keeping it warm enough? Have you had the chick all along and what kind of brooder are you using?
I took a sample to my vet, it was $25 and confirmed cocci. I had no symptoms except 3 bloody poos in as many days out of 10 chicks. I pay attention too closely sometimes. But better safe than sorry.
I have heard of Sulmet but am unfamiliar with it. Is she still eating and drinking? Not all cocci presents as bloody poos. There are 9 different strains I think. Not saying that's what it is, just sharing what little info I do have.
I wish I could be more help. At least posting will bump it back on the board for someone else to see and try to help, I hope.