I think the supplement regime you have her on is out of control. What does your vet think of it?
Also, a word of advice – your trainer is way to far away. You are putting way to much trust in others to care for her.
99.9 percent of horse trainers require monitoring and unscheduled visits to keep them training your horse. I paid big money for a well respected well know trainer to train my horse to drive. Long story short – she did very little for me. I think it ended up being very expensive board. The third month I made an unplanned visit only to confirm my concern. She had that “I have been out in this field untouched layer of dust” on her. That and all the excuses … Maybe her teeth need floating …. Etc etc even when I had left a folder of all current up to date health history, vacs, floating etc. when another boarder told me her mare had been in training for 5 years and she hadn’t been hitched yet… I was out of there. When my mare saw the trailer her ears went up, she whinnied and made a direct beeline and jumped right in… Dragging the assistant in with her. Enough said. I’ll train myself.