I contacted the FWC (FL Fish and Wildlife Conservation Commission) about the brown tint to the Wood Stork.
This is the reply I received from Adrienne Fitzwilliam, Avian Conservation Coordinator
Young birds have a faint tan tinge to their feathers compared to the adults. The adult with the tint may be a second-year bird or a juvenile that fledged earlier this year. Younger birds will have more feathers along their neck. The coloring of the juvenile in the photo looks natural for a bird of that age. Many species of young birds have a buffy look to their feathers, which they eventually replace with adult feathers.
Funny, that it's the first time I've seen that tint in all the years I've been shooting Wood Storks. Several other photographers have mentioned it also.