I recently rescued a male gsd, he is two years old and unuttered. I have only had him for about two weeks. He seems to be a really good dog and he is partially trained. however, I have noticed some behavior that I need to correct. Yesterday I was going to bathe him in my bathroom but he was terrified of my tub, so I had to bathe him outside. when I was giving him a bath he seemed fine until I washed near his back legs. He gave a deep growl. He didn't lunge, snap, or even turn toward me when he growled, but it did shock me. He didn't show teeth or seem fearful while I was washing him outside, so I am unsure of why he growled at me. should I consider that aggression? what should I do the next time he does this? how do I get him used to the bathtub? I have also noticed he isn't comfortable with the dog brush and he bites at the air when he gets excited or I am playing fetch and have his toy. I don't like it even though he doesn't physically bite me I don't want him biting that close to me. any advice is appreciated thanks in advance.