Nice plot twist at the end too. 

I'm not their social worker as sorry as I may be that they can't seem to pay their bills.At any rate, pretending to be the property manager may be a more "gentle" way for you if you just can't say "this is the criteria I must legally follow for every person that contacts me regarding this rental property".Gail

I have an STR and I'm wanting to gently reach out to newer markets. 

Both because of the fact they clearly have no interest in maintaining the exterior of the property, as required of the lease, and because they had no interest in resolving the issue of the additional people living in the house, we decided to gently suggest that they might be better suited to an apartment and that we were willing to discuss some form of negotiation to move them on somewhere else.

If they are a minority, they could even put a different twist on it that which could be worse for you.

When they pulled the walls down, lots of boards were twisted and deformed (not kiln dried).

@Sean DelagrangeI like something with a little comedic twist.

., I would suggest a security camera with some twists. 

This works if the tenant is a good paying tenant & you have to have a gentle touch.  

You could offer them cash for keys with a twist.