Ah, I see. Did you start supplementing for the latest symptoms, or did you suffer from other health issues (such as thyroid problems) that motivated you to take supplements like Iodine and selenium? I mention this because if you have hypothyroidism, it isn't at all surprising for overgrowth to occur. A low body temp coupled with impaired immunity permit the yeast/bacteria to grow unchecked. Hormonal imbalances (caused by adrenal problems, taking birth control pills, doing estrogen therapy, or perimenopause/menopause) can also make you susceptible to overgrowth.
I don't know if you can get candidiasis/SIBO all of a sudden without anything else changing (such as your general health, supplements/meds or diet), which is what it sounds like in your case since you didn't mention your history or previous symptoms. Usually, the white tongue shows up before anything severe does. I'm assuming there were symptoms prior to the latest ones that you forgot (or didn't think was important or relevant enough) to mention?