I've been dealing with yellow fungus for a while now. This is personally what I do, and it has been working. In the morning and evening, in water, I mix, acidophilus, electrolites,collodial silver and add every other day one drop per dragon a drop of grapefruit seed extract. The acidophilus (you can get that at reptilesupply.com) helps to balance the good and bad bacteria in their digestive tract. The grapefruit seed extract (get at Iherb.com)is for a yeast overgrowth. Collodial silver (get at a heathfood store or look it up online (is a natural antipathogen. It's basically an awesome all natural antibiotic.) Ok...that's the oral meds.
Topically I rub oil mixed with tea tree oil in the morning and oil with Lamisil in the evening. The tea tree oil is a natural aniseptic. Fungus doesn't like it all that well. Oh, and for those who have warts, it kills those too. Great stuff. Ok, the Lamisil is an antifungal agent. Use an oil base to dilute the tea tree oil (5 drops per ounce basically) and oil to help get the Lamisil to go on smoother. I coat the dragons whole body. Be careful around the eyes. The tea tree oil will burn. Now, the oil can be anything natural. Please don't use any petroleum based products. They are also under the names petrolatum, and mineral oil. Mineral oil sound natural, I know. Trust me, it's not. I'm using olive oil right now til my coconut oil comes in. If you want to get some coconut oil, make sure its coldpressed virgin coconut oil. If it's refined, it's healing qualities are destroyed. Find it at Tropicaltraditions.com
Hope this helps.
Jamie