I just got new brake pads installed and rotors machined. The guy at the shop says the brakes will feel a bit spongy or soft at first until the new pads wear in. When I first hit the brakes the pedal nearly goes to the floor before it will stop. But if I hit the brake pedal, let up, and hit it again it will feel normal. It's been a week now and it is still like that. Is that normal or could it be something else (air in the brake lines, master brake cylinder going, etc.)?