That used to happen to me all of the time... it is awful and would happen in the sauna or long hot baths. It doesnt happen much anymore and I think it is because of my diet changes. I used to be really low in zinc and many other minerals so whne I would sweat them out i would have nothing left. i would always get dizzy and my vision would even black out.... now that I have a very rich in minerals diet I havent had a repeat. Also...if you have Candida then you are already not absorbing minerals and vitamins as well as you should be.
So hopefully this little problem will go away as you clear up your canadida and introduce more minerals into your diet.