We have noticed Trans Union has changed their scoring model for most mortgage lenders causing a drop in TU scores. This is particularly irritating if you are approved for a loan, then before the loan is completed, your scores are again pulled and TU score might no longer qualify.
In the past Equifax scores ran lower if you have credit card debt, that no longer appears to be the case. I have several clients with significant credit card debt, no variations in information between the three credit reporting agencies, and now TU mortgage scores are running lower than Equifax.