How long have you had her, and how much has she gained in that time? Eight cups a day does seem like a ton of food, but if she's gaining on that amount (even if it's not fast enough for your tastes), it may just be a matter of her needing more time. If she hasn't been gaining on that amount for several weeks, then you want to do some more checking and consider a different food. If a stool sample turns out OK, you might look at one of the grain-free kibbles; I think Solid Gold has one, Timberwolf Organics has at least one, and there's also Innova EVO and Nature's Variety Raw Instinct (and maybe others by now, as well). These are typically high in protein and fat (like, around 42% and 24%, respectively), so I don't like them for puppies, but they should be fine for a two-year-old.