Where are you getting your scores from for this score to score comparison? I ask because I'll assume that your lender is one of the two. If the other was purchased from a service (other than anything myFICO.com offers), then you might be comparing a non-FICO score with a FICO, which can easily produce a double or even triple digit difference in score. If the 2nd came from a creditor, like from a CC approval, then know that they don't always use a FICO and when they do, they sometimes use a CC-enhanced FICO which can skew your results too.
FICO doesn't care if your loan was $0 down or 99% down. In fact, FICO largely ignore the balance on installment loans, otherwise we'd all get dinged for adding a mortgage or car.
It is possible to lose points when adding any new account including a mortgage. FICO will ding you for adding any new account because it's recent, but any ding will fade over a relatively short period of time. Usually before one year you can't see any impact.
FICO ignores your income and assets. That's a good thing. Warren Buffett has an equal shot at a high score as you do. FICO looks at your risk potential based on accounts you add, your history, and payment patterns. Because income is ignores, DTI isn't a part of FICO scoring, though lenders look at it.
