I have a healthy second calf cow in milk for about 4 months. When she just started lactating she looked fine but quickly seemed to dry up in two quarters. I checked each quarter when I had her in the chute - nothing looked unusual except quantity - no signs of mastitis in any quarter. Two quarters full, two empty - but they empty still had some milk. Calf nurses all 4. Any idea what causes this? Any experience suggesting things will balance out during her next lactation?