We did look carefully at the basement before we closed - we walked away
from a house closing a few weeks earlier due to concerns over extensive
cracking in the basement (and that house was only 11 months old!).
There was no apparent problem at the time of closing.

But then it started raining, seemingly every day now for several weeks
straight. While it could just be due to excessive rain, none the less
we feel there shouldn't be water coming in no matter the amount of
rain, at least not if they did the job right. Since the subdivision is
still under construction, we've walked through other basement homes and
haven't seen anything like this, even in the houses literally right
next door to ours.

If the houses on either side of us don't have this problem, it seems to
me like the problem is with the construction itself. I could be wrong,
but that's my first impulse.