However, this is a problem tenant and I don't want to stir the pot with him. 

Secret pot garden in the closet maybe?  

Nothing major - a fun-colored pot, dish towels, a bowl of colorful fruit and flowers in the kitchen; a shower curtain and towels in the bathroom; etc.

a landlord can prohibit renters from growing pot by including the rule as a clause in the lease.

If I were you I would offer them 3 free months to move out voluntarily with notary; and file that agreement with the court.

Maybe see if they will leave voluntarily.

It is like having a bunch of strangers having the power to interfere with your investment.And then there are the board members who decide it's their mission in life to harass owners/tenants about every weird thing, like potted plants on the balcony or whatever.I only bought the one condo, intending to keep it forever and rent it out.  

In this situation, the tenant has been paying and so it would be the tenant voluntarily moving out with some upfront $ (when contract is signed) and then remaining $ once he's fully moved out.  

Look for physical evidence of pot use.

Fourth, add a few decorative touches to make the home more appealing: Place a flower pot full of marigolds or brightly colored welcome mat by the front door; Set a colorful bowl of fruit on the kitchen counter; Install some decorative shelving on bathroom wall; Paint one of the walls in the living or family room an accent color that harmonizes with the rest of the room.Fifth, learn to live with and accept what that renter does with YOUR house.