The trouble, in general, with replacing or altering a poll with substantial participation is that many of the voters who already voted will not vote again in the new or modified poll. You could just carry the tally over, but then some of them would presumably have voted differently had the new option been included.

So the options are to throw out data, or to incur inaccuracy. Neither is real good, although I think most would agree the former (i.e. close this poll and start a new one) is clearly better.

A better option would be to start a separate poll for whether they should be changed or not. You, or anyone else wishing for no-change, could certainly do this at any time, and I'd expect the two choices ("change/no-change" and "given change, which change")to be rather orthogonal, under which reasonable extrapolations are possible