Thye new 7 Mile Market has a large selection. In the deli department some of their dold cuts are GF too.
Close by in Colonial Village Shopping Center on Reisterstown Road there’s a SunSplash natural foods store that has some gluten-free things (check the freezer cabinet too.)
I think there’s a place in Rockville but I’m not sure. The DC area is getting quite frum-friendly these days, with less and less need to trek up north to Baltimore.