Feeding suggestions for my TB?

Hi im looking for some suggestions on what to feed my horse. He is a 9 year old TB in medium work, he is prone to getting himself a bit wound up and stressed over silly things so I need a diet that helps cool his hot head but also helps him keep his weight and condition. I am feeding him a combination of pasture mix and Dengie fibermix easy in the summer and pasturemix, fastfiber & speedibeet in the winter. Is this a good mix for him or should I change it? Any suggestions welcome thanks