Tail turned white

Hi. Maybe someone knows. I have had my new dragon for a few days. And his tail turned white, as well as his mouth. What could it be? (he has uvb and heat lamp, the temperature during the day is about 43-46 degrees Celsius (103-115 degrees Fahrenheit), we also turning on the heat mat for the night (25 degrees Celsius(77 degrees Fahrenheit), eats crickets, super worms, salad, we powder calcium with D3). He is acting active and doesn’t show any signs of illness. I’m very curious