Q.Brussel Sprouts
My plants have gone to seed. What do I do?

It is common for young Brussels Sprout plants, when exposed to cold temperatures (below 50 degrees for a period of time) to bolt.
You can look for seeds that are bolt resistant.
Your plants can be pulled up and you can plant again.
https://www.gardeningknowhow.com/edible/vegetables/brussels-sprouts/brussels-sprouts-problems.htm
https://www.gardeningknowhow.com/edible/vegetables/brussels-sprouts/how-to-grow-brussel-sprouts.htm