I think there is a convention in absentee ballots that if the vote at the meeting was such that there was a majority big enough to mean that if the absent members might, if voting unanimouly, be able to overturn the changes, then I think you are expected to send another ballot out.
If you had instituted proxy voting, proxies could vote at the meeting,
This is probably in Robert's Rules of Order. Many associations don't even attempt to go by those rules, but it is best if you do.