I agree with all of the above, but a less expensive, more simple possible fix could just be finding the right hoof oil/moisturizer for your horse’s needs. My horse had a similar issue in that his feet were very dry and cracked, and he had very soft, tender heels. I was able to fix this simply by picking his feet, then applying Farrier’s Fix (which is moisturizing and hardening), as often as possible and I have noticed a world of change. He is no longer sore or cracking feet. Something similar to this might help you, I know Hoof Heal works well on dryness, and Hooflex magic cushion has provided him with relief from soreness in more intense cases, and even fixed a case of lameness.