Bred horse max health changes some time after being tamed

Breeding horses, trying to get one with max hearts, speed and jump height.

But many newly tamed horses show some or much of its health as empty hearts.
These horses:
- before fully grown, were never hit/injured at any time
- will not eat food once old enough to tame
- feeding and not feeding any food till they were adult size made no difference
- splash healing potions don’t fill the empty hearts
- were enclosed in a small fenced area with 2 hay bales per 4x4 block area as they matured and once tamed
- riding 1000’s of blocks did not replenish the empty hearts
- afk-ing overnight sitting on the horse did not replenish the empty hearts
- all had signs recording total amount of hearts upon being tamed, with a saddle left on each tamed individual

These empty hearts always disappear if the horse is not ridden after a short amount of time.

*ps, huge thanks and appreciation for correcting the achievements glitch in the latest update 😊