As I understand you:
1. There are 6 lots in all and
2. The 3 member strata committee (that existed prior to the AGM) want to remain in place for another year, to the exclusion of the 3 other lots who want to sit on an expanded committee.
If so, in addition to the recommendations by Jimmy, you could seek mediation on the matter by calling NSW Fair Trading on 13 32 20 and they can guide you on applying online. You could allege that the committee is breaching
s37 Duty of members of strata committee
“It is the duty of each member of a strata committee of an owners corporation to carry out his or her functions for the benefit, so far as practicable, of the owners corporation and with due care and diligence”.
You could allege that limiting the committee to the same 3 people who comprised the previous committee benefits only those 3 because half the OC is impeded from carefully examining what exactly took place in the past and the same 3 it seems want to continue with their secretive conduct.
“What exactly are they trying to conceal” you should ask in your application to NCAT.
238 Orders relating to strata committee and officers
“1) The Tribunal may, on its own motion or on application by an interested person, make any of the following orders—
(a) an order removing a person from a strata committee,
(b) an order prohibiting a strata committee from determining a specified matter and requiring the matter to be determined by resolution of the owners corporation,
(c) an order removing one or more of the officers of an owners corporation from office and from the strata committee.
(2) Without limiting the grounds on which the Tribunal may order the removal from office of a person, the Tribunal may remove a person if it is satisfied that the person has—
(a) failed to comply with this Act or the regulations or the by-laws of the strata scheme, or
(b) failed to exercise due care and diligence, or engaged in serious misconduct, while holding the office”.
If you argue that the 3 are not benefiting the OC (that is failing what is required under s. 37), you then can also allege that all 3 need to be removed because they breached s. 238 (2)(b). Specifically, argue that their united behaviour demonstrates a wholesale failure of diligence inasmuch as the 3 exhibit an inattentiveness to the needs of 50% of the owners.
In the ideal world, the 3 will be ejected from the committee and the other 3, including you, will become the committee.