What I'd like to know is how is it being treated for parasites? what's the dosage you are giving it? what drugs? where did you get the info to give these dosages? Are you sure thats the right dosage for that species? are you treating it for the parasites that it has or are you just doing a shotgun approach? If the former how did you find out? can you tell me what it eats? what's the latin of this species? What ph level should the water be at? do you have it's water filtered? does this turtle need a dry area to bask in? how often are you changing the water? is it male or female?
You said you did your research, so you should know the answers to the above questions.