I would take away the sweet feed. Sweet feed is very unhealthy for horses, it is full of sugar, and minimal fat and fiber, which is typically the healthiest and fastest way to gain weight on horses. Beet pulp and rice bran are high in fiber and fat, and may be a good choice. I would get them on free choice grass hay (due to you seeming to have snow on the ground), either on the ground or in a small mesh hay net, possibly with some Alfalfa hay.
Other than that, looking great! Congrats on rescuing them!
“Good things come to those who wait… greater things come to those who get off their ass and do anything to make it happen.” - Unknown