DA approved landscape plan

We recently planted new shrubs within concrete planter boxes at front of building so they are on strata land.

The developer contacted council to complain that we have replaced the two year old shrubs half of which were dead and the rest just ugly. Council have told us we are in breach of the DA because the approved plantings must remain for the life of the building and is therefore a Contravention of the Conditions of consent. My question is

Does a DA and condition of consent remain two years  after the developer has sold the lots ? Are owners then responsible for the CP gardens that must not change (from original DA) for the life of the building ? Does responsibility transfer from developer to the owners after Occupation Certificate has been issued.