Did you read the label on your borax cleaner? Did it contain anything else such as chlorine or parabens?
Ordinary borax(sodium tetraborate) is very safe according to its Material Safety Data Sheet(MSDS) - borax is about as poisonous as ordinary table salt.
You could also use boron tablets from a health shop -- these will be expensive -- but these are given in tablet dosages of only 3 -- 6 mgs and you will need much more than that to kill the candida. In proper dosages, Borax also helps to balance the hormones, stops and reverses osteoporosis and arthritis and helps to remove fluoride safely from the body(fluoride is an acidifying root cause of candida). See this link on arthritis: