Different rents on sides of duplex?

[Seth Levey]

I have a duplex with identical 4/2 units. One side is renewing this summer and I've told the tenants their rent will be $2100 per month for next year. The other side lease ends a few months later and the current tenants will not renew so I'll have to place tenants. I think market rent is more like $2200-2400. Can I rent the identical other side at the higher rate or would that violate fair housing laws or something else? Even if it's not illegal, it may create bad blood when the tenants inevitably talk and realize they're paying different rent. Thanks BP! Seth