You're so very wise to have taken a bird in. That's great chicken stewardship! Thank you for that.
As for the candida, probiotics and organic apple cider vinegar in the water (1 tsp/gal of water) help directly, particularly if you can get a probiotic that has bifidobacteria in it. (For individual birds, oddly, check the health food store for probiotic treatments for yeast infection). Some yogurts have that as well - check the label. I think one of the activia has that blend - lactobacilli and bifidobacteria.
If you want to avoid a lot of dairy, try Probios dispersible powder from the feedstore. Beneficial bacteria help reduce the chances of the single-celled candida from morphing into the multi-celled pathogenic form.
If you use a medicine for the candida, be sure to ask for diflucan over nystatin. Nystatin works best with an empty crop while Diflucan doesn't require it and is much more effective. Just a heads-up.
I'm glad you got SOME answers at least.
Did you need information on vaccinating all incoming birds for marek's? If you do, Dr. Peter Brown at First State vet supply has a great article, as does K T Thompson.