Grassy brassica questions

I got in a big hurry this year planting brassica plots. (new baby may have tangled up a bunch of summer "fun" at the farm) My brassica plots are experiencing a good deal of competition from grasses. Can brassicas be sprayed with a grass specific herbicide? How much competition can they take from grass? Is it best to just live with the status quo? Thanks in advance for your insight.

Grassy brassica questions