How would you feel if you found out now that the Vice Chair or Clerk had invited one of the other candidates to tweak their submission, after the deadline, if they considered that it wasn't sufficiently robust in its original form? More importantly, how would the one unsuccessful candidate feel? You're lucky your submission wasn't excluded from publication, as there are no official rules for this type of exercise, so unless your council has an agreed policy, they can make it up as they go along.
As Mrs Abster has said, most councils would steer well clear of any involvement in a public election.