I do have left-over batter since I only cooked for two people; should I add a touch more baking powder this evening when I make them again? Thank you!

You will probably need to, but it would be worth cooking off a small sample before you add in any. Baking powder doesn't all work immediately, and not all types lose potency at the same rate once mixed. The most common sort, labeled double action- work a little when moistened, and the rest when heated. If you used a single action type, then of course- most of the leavening action would be gone entirely. Once you test cook a sample, you will see if it's all gone entirely or perhaps you just need to give it a bit of boost.