I think the principle of “buyer beware” applies here. I’m not a lawyer but I think in theory that the new owners should have realised through the property inspection that the bathroom had been renovated and through strata searches that the vendor had not received the appropriate permissions.
So you could ask them to agree to a by-law transferring responsibility for the renovations to them.
Or you could pass a motion declaring that there have been illicit renovations in the property and that the new owners will be responsible for any repairs and maintenance required moving forward. If there are any repairs required after that, then they can chase the OC for payment, rather than the other way round.
At least that way it will be on the record that the new and subsequent owners can’t expect the OC to fix the bathroom if repairs are required.