This is overpowered as is for a common, if you were to limit it to a specific creature type - probably Cats - a la Veteran Swordsmith & Veteran Armorsmith then it would be OK. And you could drop the cost to match () as the P/T is already the same.

Why is this overpowered as a common? Veteran Swordsmith's only difference is in being soldiers-only. But, it's costed [1] less to match.

blanket pumping of only your own creatures for more than a turn is just not a common ability. You could maybe get away with it at common if its cost was - making the extra mana in the cost into white mana. As is, its too easy to splash into just about any deck, especially in a limited format.