Tenants complaining about smell of marijuana

[Yi Zhao]

Hi BP,

I have a house in College Park, MD. It has a separate upstairs and downstairs unit. The tenants downstairs have complained of marijuana smell from upstairs several times already. At this point, the upstairs tenants are denying it (all kinds of excuses). 

I've tried several times getting them together and talking about it. Although the tenants are very nice about it, the downstairs tenants keep smelling it. 

I'm not sure what else I can do at this point. Any advice would be greatly appreciated!

Thanks, Yi