Have you looked at all aspects of your situation? Holistic care does not just mean health. Holistic care also looks at the dynamics of the daily routine of your horse. Maybe it is time to review your feed, add or remove supplements, check your equipment fits (again yes!), get your horses teeth checked (naturally if necessary also have them done).
Tip 2 – Ask experts! This is not to undermine your knowledge, but there will always be someone who knows more, that is their profession! Plus there is a feeling of satisfaction when you call an expert to review teeth, equipment, feed etc. and they tell you that you are doing the right things!