Note these points are not underneath the hoof but on the top surface;
The horse has acupuncture channels which run down the leg. These all end near the coronet band on areas called ting points. If the energy in a channel is weak or blocked it does not allow the chi and blood to move fully down into the hoof. And then that section of the hoof does not get fully nourished with blood and so does not grow so well. This gives rise to hoof imbalances.
For example; sometimes the toe on the back grows too long.(this gives rise to forging or overreach.) Actually it is the heel that grows to short. If you stimulate the ting points on the back of the heel by one off acupuncture or regular acupressure or laser the hoof will grow regularly back and front.
Anohter good tip is to look for hoof cracks. These definaitely start happening when the chi in the channel is weak and not strong enough to push the blood into the hoof for growth in that area,