All the snapdragons I purchased in the fall and planted out are done. They've all turned brown and I'm pulling them out.

You might still have some time left for yours since you're further north (I assume from your zone.

Are the plants them selves still green?

I'd cut those brown parts off. We've always been told to cut the blooms of annuals when we plant them so they'll put energy into growing roots and not blooming. I've never been able to do that. :(

If you do not cut the spent flower the stem of that bloom will die back to the plant. Your snapdragons will bloom non stop thru the summer into the fall, if you dead head. I go out once a week just to dead head my snapdragons and gerber dasies. I either just snap off using my fingers, or use kitchen sizzors. My snapdragons bloom non stop. I started with the $.25 plants and they are now larger then dinner plate size. I always put mine out in Oct, and put them under hugh oak trees, they love it down at the coast, and the wind doesn't seem to bother them. Barbra