I wouldn't think candida would have anything to do with your low cortisol level.

I am only familiar with Diflucan to get rid of yeast. It is hard on the liver so I would avoid it if there is no positive reason to use it. Ask your doc if candida is a possibility. I have used Nystatin (liquid swished in the mouth) a couple times for Thrush caused by not being careful enough with my steriod inhaler.

I believe the best way to test for addisons is the ACTH stimulation test. You can have a low cortisol level one moment & not the next, so one saliva test means little.