You have the distribution down pat. The only known calving grounds are down off the coasts of Florida and Georgia. The animals migrate up toward New England and Cape Cod Bay in the spring. They have just departed that region and are now, as usual, heading across the Gulf of Maine and just starting to show up in the Gulf of St. Lawrence.
Again, because we can identify these whales as individuals, we have a good sense of who is actually in the Gulf of St. Lawrence or elsewhere. It's slightly less than half the population annually. About 140 or so individuals have been returning to the Gulf of St. Lawrence on a pretty regular basis since 2017. That is a direct result of very thorough surveillance efforts by DFO science and NGO research groups like the Canadian Whale Institute. Also, NOAA in the U.S. has a survey plane that comes up for a few weeks each year to help with the count.