I would say, probably it is too late.
It should be around your FF time. Is it ?
I find fall planting very tricky. You start too early, then it is too hot. You start later, then it is too late. I think brassicas are long term cool crops. Therefore spring planting gives the a chance to grow, provided it does not get to hot, causing them to bolt.

If they are close, They will stand into the low twenties, so you you still have a fighting chance to get heads.

This close , maybe {{gwi:114259}}

Thanks for your responses. Our average first frost date is October 15...We have had one night go down to 31 so far. At least the plants look good..Just like the picture you posted, farmerdill. I grew fall broccoli one year and it was the best I ever tasted. Finally tried it again and I thought it would be easy...!