I'm not an expert on cherries, but I have a good bit of experience with young trees. It is possible that they were mislabeled, the #5 usually refers to the size of the pot that the plants are in, not the cultivar. That being said, don't fret too much about them not blooming or putting on growth at exactly the same time. They are not fully mature trees yet, and there may be some micro-climate conditions, or soil conditions that make one side of your yard different from the other.

There is a row of Bradford pears near my work office that were all planted at exactly the same time, they are all supposed to be the exact same cultivar; however, they do not all bloom or leaf out at the same time every year, (one is consistently about 2 weeks later than all the others, and these are mature trees).

Even if they are not the same cultivar, I am assuming that they are strictly flowering cherries, and were purchased for their blooms rather than any fruit they might produce, so synchronized blooming is not that important; (it looks great when they are all in bloom together), but it isn't critical to the health of the trees.

Sorry for the aeons late message but how'd this turn out? I have a Yoshino that's behaving the exact same way, it got buds and then just stopped