At 2 1/2, she should just now be loosing here first set of incisors. I can't really imagine that nutrition plays a role when they shed their teeth. It's going to happen when it's going to happen.
As far as feeding her a senior, keep in mind that it is a complete feed so the nutrients are going to be diluted with forage therefore requiring more to get the same total amounts. It's also formulated for an older horse's nutritional requirements and if most notable lower in Lysine, Methionine and Cystine. These 3 AA are important in growth and development. Your alfalfa cubes are also going to be less nutrient dense than alfalfa hay as most cubes are made from lesser quality, lesser eye appeal hay. But that's not a bad thing now. Build her up slowly. The mineral block is another matter. If it's the traditional brown trace mineral block, it's pretty much useless as it's 99% salt. She should be getting a product that is 15%+ Ca and roughly 8%P.(you want twice as much Ca as P) It should also have a good Vit A (min 100,000 IU/#) and that will clear up any rainrot. I personally like the Moorman's and Progressive mineral products that are designed to be fed with grass hay. You can also go with just a ration balancer (Enrich 32...) but the loose is the cheapest way to go. I just hang a bucket with about one pound of the product by the water tank.
If she did grow 2 inches in a week, than you need to cut her back to nothing but grass hay and a mineral/vit supplement. Otherwise, leave her where she's at for a month at least. She has the potential to grow until she's 5-6 so stretch it out as long as you can.