Feeding my QH. Does anyone have advice?

Currently my QH is ridden three times a week. On a Thursday I ride for 45-60 minutes in the arena doing dressag or small jumping. On a Saturday I ride for about 45 minutes either in the vineyard where I do mostly walking but also lots of uphill trot and canter work. And on a Sunday I generally ride for around 2-3 hours. We do a long trail ride in which we do lots of walking on different terrain and different places all the time. We also do trotting and cantering a lot.

Currently it's winter, the nights are around -2 to -5 celcius at the moment and the days are around 14-15 celcius. He is in a 300 gram fill synthetic rug on at night but during the day he is naked.

He is fed 3 times a week, his hard feed, which consists of 1 scoop of wheaten chaff (a scoop is just the normal scoops that you buy from a saddlery), half-3/4 scoop of Hygain Ice pellets and 1 cup of Speedi Beet. He also gets all necessary vitamins and minerals.

Everyday he gets 1 flake of grass hay in the morning and 1 flake of meadow/clover hay in the evening. He is a good weight at the moment and looks healthy. Although I'm open to any changes in his diet to make him healthier or that are good for him.

So of anyone thinks anything needs to be changed/stopped/added in his feed please let me know.

Also just a note he is prone to foundering and he is all English ridden just in case it matters.