Differential Maintainance charges

Hello. I am residing in Lilleria avenue, newly built flat scheme in vadodara. Our builder handed over collected maintenance charges to society, where some of residing member have taken up charge. they have not formed any legal society (not registered under society act, 1960) but managing more on personal relationship. My flat is rented. But since last few months they have made new policy, where maintenance charges for residents are same as per previous. But for those flats which are rented they have increase maintainance charges by 40%. They dont have any logic behind this, except they think rented flats can afford more charges. This is absolutely illogical, burdening us with unnecessary maintenance charges. upon objection, they have taken voting system where majority was in favour of this decision. Basically there are only few rented flats and majority are residents. So this is implied. But this is surely indicating unjustice & differential treatment to rented flats owner. Please advise how to take up this matter legally & make it equal for all.