Yes, the new account and your new car both dinged all 3 of your reports probably by similar increments. The car and new account will hit your report as each lender reports to the CRA. Most lenders report every thirty days. You can find out when by just calling the lenders and asking them.
The others are correct as to why your score went down. Opening the the new account and buying a car within a short amount of time of each other could have cost you up to 5 points for each inquiry (inquiries = 10% of your score) even though two per year is moderate openings.
Also, if you are using more than 20% of the available limit of either your old or new card, that could lower your score by several points (utilization=35%). However, your score can quickly rebound (even within 30-60 days) by paying your cards down to 20% or less than the available limits before the next time the lenders report to the CRAs. But since you don't plan to use your credit until next year to buy the house, you can take some time paying the balances down as long as at least 2-3 months before you actually apply for the mortgage, you make sure the utilization is under 20%.
Also, your 11 year history suffered because the new accounts lowered your average age which meant you probably lost a few more points there too (aging=15%). This is a long shot, but do you have any accounts over 10 years old with zero balance that you were not using? Sometimes after 10 years of inactivity, dormant accounts with zero balance fall off your report. If any of your older cards have fallen off, even though you have been using credit for 11 years, your aging is now being averaged based on the age of the oldest card remaining.
I hope this helps.
