I have a 4 month old Newfoundland puppy. Recently he has started to walk differently. When he takes a step with his hind leg he twists his foot and drags his pads across the ground. After a while walking he has worn down his outer most pad to the point where it is bleeding. Could this just be because he's growing quickly and needs to adjust to his ever changing body? Or could it be something else. We go for a walk everyday, about a km long. Thanks in advance.