Seems like a very low bar for being able to increase the maintenance fees, in the sense that a quorum only requires 51% of the building's units be represented. In addition, it states in our regulations that one individual can represent up to 3 owners at these meetings. Then, the majority vote is only 50%+1 of those present to make up the quorum. So in total, you could have a situation where not even a real majority of 51% of all of the units in the building complex approve the increase through the resolution at an Assembly meeting.
Moreover, our regulations state that they must demonstrate the numbers in the meetings that voted for and those that voted against any one resolution. Under the resolution to increase the budget and monthly association fee, it merely states that there was a majority in approval, but no details of the numbers that voted in affirmation and those that voted against the resolution. To me, that seems grounds to challenge whether the resolution was actually passed at the meeting and/or they need to do it all over again at another meeting.
Finally, I get the impression that they went searching for signatures after the meeting to make the 'asistencia de nomina' look like it had a quorum and that is obviously not permitted in the condo laws of 1958 and our own regulations.