There’s no such thing as keeping them at a good weight. A weight which is good for one piggy is not right for another - their individual heft is the indication of what is good for their own personal body condition because piggies come in different shapes and sizes.
Their diet needs to be unlimited amounts of hay. Veg and pellets are snacks and they can be fed 50g of veg per day and just one tablespoon of pellets per day and have unlimited fresh filtered drinking water. They will then find their own natural weight in their own time.
Do check their weight again - they could not have put on 1lb (450g) in one week.
As far as I know they are a good pellet (i believe is more popular in the US than here though).
Do just ensure you keep them to just one tablespoon of pellets per pig per day. They must not have unlimited pellets
Did you check their weights again? They couldn’t have gained 1lb in a week