I am in the process of building a house and had the drywall taped and textured.(Approx 2 mo. ago). Now it appears that at several seems there is a crack forming. What is the easiest way to repair this crack. Both at the peak of a vaulted ceiling and at another joint in the ceiling. What causes this to happen. I know the drywall has more that the appropriate number of screws to hold it up. Could it be moisture? The type of mix for their tape job? Please help.