We know but can’t prove who the perpetrators are, and some owners are getting frustrated.
This is the key. There must be some way that you can prove who is doing the smoking. If it’s on another balcony, set up a spy-cam on a (friendly) building opposite. And no, before we get the privacy argument, it’s not illegal. You can photograph or film anyone anywhere provided it’s not for sexual or illegal purposes and you have the permission of the people on whose property the camera is situated.
But to answer the original question, you can’t stop people doing what they want in their own lot if it’s legal and you can’t show that it’s harming other residents.
Which brings me back to my first point …