I have a 7 YO racing AQH. He's currently in race training so he's being exercised a couple times per week. He's is in great shape! But now, he won't eat :( he'll eat hay and some alfalfa but no grain. He's currently on Omolene 200. And he gets his doses of vitamin B12, complex-B, and C. And also iron supplements. He hasnt been eating (besides hay) for about a week. I don't want him to lose weight cause then it affects his exercise. What can I do to get him to eat? Or what's going on with him?