New house, where are my kittens peeing?

We just moved from a small apartment into a house, and I've noticed a sudden drop in the amount of pee in the litterbox (2 kittens, 11 months old).

I've searched the house and I haven't noticed any puddles or strong pee smell... Is it possible they're just peeing less because of nervousness? Or are they probably peeing somewhere in the house?

The basement had a definite cat smell when we moved in (from the previous owners), but like I said, I can't detect that the smell has increased at all since we've moved in, and I can't find any obvious pee anywhere. And we haven't caught them peeing anywhere.

Any guesses? Should I be worried? We never had any pee problems at the old apartment, except for one or two isolated incidents due to nerves or illness.

chris.

Maybe a dumb question, but do they know for sure where their boxes are now?

Yes, they use their boxes for #2. It just seems that there is a marked drop in the amount they are peeing, which worries me that they may be peeing elsewhere.

chris.

Are they eating okay? drinking enough water? running and playing? I would think that if they're scared or nervous they would be doing their toilet in other places and more often.
I would not worry too much as long as they use the box regularly and have no health issues.