Hello, My silver-laced Wyandotte is about 3 years old. Lately she has been listless, with a sunken head, runny/smelly vent, and not interested much in eating/drinking. I thought it was coccidiosis, and we have been giving her sulfamethazine sodium for a few days, but she doesn't seem to be improving. I'll continue on the medication for a few more days. What else could this be? Should I try a different medicine? Thanks for any and all responses!