You have a pad or piston hanging up and not letting the pad off the rotor surface. Brake fluid if left un changed for too long can draw in water and cause corrosion in the caliper that causes this. the other possibility is that when you ground whatever down you damaged something.
Grind something off the Calipers? That does not sound right? As others have said, sounds like you need to service the calipers.
Are you mechanically minded, or would you have a Garage perform the work? At the end of the day its a Brembo Caliper (presuming your calipers are stock?)
I put new pads and rotors on my car in March. Stop tech slotted rotors from rock auto and Hawk HPS pads. One of my front pads is almost gone while the other has more than half left.
I do remember that when they installed my brakes they had to grind something off my calipers to get the rotors to fit. If this means anything.