You could ask your strata manager or strata committee to send them a letter simply reminding them that
a) there is a standard of behaviour on common property set in the by-laws of the building (with the relevant by-law quoted), and
b) all residents can be fined for breaching by-laws, and
c) that a breach of by-laws may constitute a breach of their rental agreement (in which they have agreed to abide by the by-laws of the building) which could give their landlord grounds to cancel their lease and evict.
That’s all they need to say, without making specific allegations. That said, this is just as likely to inflame the situation as resolve it.
Maybe you should just keep your mobile phone handy and pull it out, saying “I am recording you” very loudly. Privacy laws only prevent you from recording people secretly.
And, if you really want to record them, there are apps available that put your phone on to record instantly at the touch of a button.