Delinquent fee interest

We have had three MC in less then two years....each year there has been many delinquent accounts..MC #1 charged interest at 18%(allowed in FL) per year 1.5% monthly...MC #2 charged the same interest some time and to some HO's and not others and would also skip some months completely...MC #3...hasn't charged any interest, even to delinquent BOD's....but have sent collection letters to HO's that some have interest added from previous MC's and others don't (carry overs from the two years before and are still delinquent.).....I had a meeting w/the MC and ask about this and was told they were waiting for the Board to tell them how much and if they wanted to add a late charge as well. Right after the meeting I relayed the message to the treasurer and she called the MC that day. The MC has had our Association since Oct/07. I told her the Association could be sued if ALL HO's weren't being treated equally as far as collection. That the MC or Board can't pick and choose whom they want to charge interest to or show favoritism. I am right about this, aren't I? What if anything can I do about this.