Hair loss on back?
So the other day while brushing Brody down I noticed a large amount of hairs coming off his back. I brushed all the hairs off with my hand and noticed that his fur is very thin on his back about 3 inches from his tail. It's thin enough to clearly see his skin and feels more coarse than the rest of his coat. It's a bit concerning as the rest of him is nice and full and still very much puppy soft. Any suggestions or ideas on what might be the cause of this? I feed him wellness super 5 mix lamb formula.