i would give 30 day notice now
so it is like 60 day notice. You will increase rent to 1200 or 1250. If tenants don't decline, lease will end on 9/30/17. I did that when I purchased last property. Tenants know they are paying lower than the market rate so either they stay or they leave. if they leave, you find new people which is better because you can screen them and find good tenants yourself.