I use Borax myself but only for the Boron content and not fighting Candida. I use 6 grams mixed in 1.1 litres of distilled water which gives 3mg Boron/5ml teaspoon. You might be overdoing the Boron. I do not know what weight of Borax there is in 1 tablespoon but it sounds very high. 1 tablespoon of the dilution does sound quite high a dose of Boron. The maximum is meant to be 20mg/day and I have been going above that so I bet that your taking far higher than that.
BTW you are not going to beat Candida by doing this because the cause is not Candida, it is a bacterial infection. Shhhh don't tell everyone ;o)