The cracks display no apparent displacement, but the concern is that they have occurred right under a major support beam. You should bring this to the attention of Beazer and discuss it with their engineer (not their sales staff). You can, and perhaps should, hire your own inspector or engineer to evaluate the situation on your behalf. The city inspection department might also be of assistance to you in the matter. If the cracks are a structural concern, they can enforce a proper repair.

Those cracks don't appear to be minor. You must have them check by a structural engineer.