Refinance effect on New Build Property Taxes- HELLPPPP!!!

[Kyle Agius]

A bit of a long story so I am going to structure this by first asking my two most important questions, followed by the situation and a few follow ups.  Any help is much appreciated.

My underlying questions are:  

1.) Will a refinance of my newly built home (6 months post closing) cause the property taxes to increase on the newly increased appraised value?

2.) Will the city come back to us whenever they reassess home and ask for backdated taxes from when the home was sold to us?

My wife and I finished building our home in denver about 6 months ago through Oakwood Homes.  Since closing, we have been paying property taxes based on the value of the land alone (~$130k) as this was the assessed value. I now went to refinance my home bringing my rate from roughly 4.37% to 3.99% and was required to have an appraisal completed.  My mortgage broker running my refinance informed me that my property taxes may increase to cover the new value of the home ($430k). This equates to about a $300 month difference between the current amount paid and the new required amount.  Imagine that the assessors office does not do a reassessment until mid 2021.  The math there would have the city coming back to me and all my neighbors for $7,200- something that i cannot imagine them successfully doing. 

Does any expert out there have answers or any advice into this?  Please ask any follow up questions needed.  Thank you all so much in advance!