I am considering switching my horses feed... Which have ya'll tried and had success with?

My filly is just a little over 3 years old (And 16 hands) and is ridden fairly lightly, but she loves to run and buck and bite the other horses in the pasture. Every time she grows she gets super skinny, and then plumps back up super fast when she stops. She is fed high quality Orchard gr hay and gets 5 flakes a day. I am seriously considering Omolene 100, Nutrena's Safe Choice or Nutrena Life Design Prime. Any other suggestions? She now get 4 cups of oats with 4 cups of rice bran and a scoop of Horse Guard.