Thanks for the link barnyard.
CoopMOM I replied to your other thread too.
Mix it up at 400-800mg/gallon then and let her drink at will. Per bird consumption isn't going to be listed because chicks to adults, banties to standards are going be be from half an ounce to 13+ lbs. The "dosages" are going to be a flat rate and based on the water they need to drink. So just mix it up and let her at it like you would with liquid sulmet.
I would get fecals done before treating further. Oh, and if the other bird wasn't sent to necropsy, did you at least open her up to see if there was something going on inside? I'm of the camp that antibacterials are usually not the answer and really just make things worse in the end as it's an indiscriminate killer of the 99.9% of the good bacteria you want around.
Good luck.