Raising rent on tenants that come with the house

[Dan Costantino]

I just bought a duplex fully tenanted. Market rent is $600/unit. It is rented for $425 and $475/mo. The $425 tenant has been there ten years. They have accepted an increase to $500/mo. I haven't talked to the other tenant yet but I'm thinking $550. Am I being a wuss by not moving them to market rents? The leases are up at the end of the month. They both pay timely so I don't really want them to go. Thoughts?