I would first cut out the daily dewormer. Rather do fecal testing and deworm according to what needs to be targeted.
The grass pellets are better replaced by alfalfa pellets, since she needs to gain weight anyway.
As for a vit/min supplement, hit the online vet supplies. They have a huge selection and the analysis is usually there, so you can compare.
Lack of sodium is the easiest to take care off. 30g daily of iodized tablesalt in the feed, divided over her meals, and a salt block, straight salt, white, or the Himalayan one.