bald spot

Two days ago I noticed 2, quarter size, areas on my fawns back about an inch from the base of his tail where his fur was falling out but also the skin was flaking off with it, I could see what the flakes of skin on the fur as I was very easy able to slightly pull on the fur and it would come right out. The skin is just the epidermis because there is not sores or bleeding. I approximated him to be about 3 wks when I got him, so that would make 6wks now. I let him do most of his own grooming and he does well. The only thing I do is clean milk off his face after feeding, and clean any dried feces with hypoallergenic baby wipes, and Ill use a Sullivan's shampoo when he ends up laying in his pee, i have been using puppy pads because I have him in the house and they do not always soak up all of it. He is also in the AC but I run a humidifier about 6 hours/day for him. I have not seen him chewing nor do I see any bugs on him. I did give him 1cc of Tylan 50 antibiotics,and of course probiotics. I cleaned the areas with witch hazel and but some mineral oil on it, that way it was all natural so I did not worry if he licks. I am going to try to attach a pic, if any one as an idea of what this could be and what I should do to treat it please let me know. I care for all kinds of orphan and injured wild animals but I have not had a fawn for many years.

I am trying to get the picture of the memory card of my camera. I will try I get it up asap

Thanks so much, I will try the black light, but I am thinking it might be a Vit. D issue. It is not spreading but he losses his fur pretty easily, and right now I am dealing with another spat of diarrhea, the worse it has ever been, this morning was the most solid I have been able to get his stool in 3 days. I have re-wormed and started a round of antibiotics. But, this is an issue that calls for a form all its own. thanks for the help.