So two things.
First, were the garage and sunrooms additions to the original structure. You may want to contact the county to see if a permit is on file. If those are, in fact, unpermitted additions, the appraiser will not capture that square footage. You'd do well to have those areas inspected and get the work approved by the county.
Have you checked your own credit history to see if anything is being reported without your knowledge? If the issue is debt to income ratio, something may be reporting in error.