They don't seem to have any effect on digestion or stool consistency, although you should always watch for negative changes when supplementing the diet. Give the supplements about a month to give her some relief. If this doesn't work, you may want to consult your veterinarian. Three months ago I had minor surgery to remove a growth on my shoulder. Everything went fine with the operation, and the wound has healed nicely, but my hair hasn't grown all the way back.
New hair is fairly fragile, and can easily be broken off by biting and clawing.
Even something simple like discontinuing a supplement could account for the hairless area. Try adding a fish oil or vitamin E additive to your diet. Lately, she can't seem to keep up, and pants for hours after we get home. She's only 2 years old, and in very good shape. While there is no way for me to tell if she's in pain or not, I would bet that she is severely overheated.