Maryland is going through some of the same problems as other states in New England: high taxes and property prices are driving people away. Many retirees are deciding to settle elsewhere, but that hasn't necessarily caused home or apartment prices to fall. Maryland is also a really small state so there isn't a lot of room to go around. Maryland's population shrank in 2023, but it was rising a couple of years prior.
Still, it looks like it may have been the start of a long-term decline for all of the reasons mentioned above unless some changes are implemented pretty soon to lower the cost of living.