If you have another good spot for them, it would be better to rotate the beds, say every 5 years.

Doing this, you can amend the new bed with lots of compost and organic material in a way you can't really do with an existing bed. It will also be free from old leaves and other strawberry debris that carries mold and disease.

If the current bed is your only good spot, you can dig up the old plants, amend the bed, and replant, but as the old plants aren't producing well now, it would be better to discard them.

In either case, Instead of cutting off the runners, root them and move them into the new bed early this fall, which is the best time to plant strawberries.

I am having a terrible time with my strawberries. I had a huge growth of beautiful plants. Had some great berries and picked them through May and most of June.
Now if you look at the bed you would them someone hit it with a flame thrower. 90% of the plants are totally brown. There are a few green leaves on a few of the crowns but I had hundreds and now I would be hard pressed to have 20 plants.

Any ideas on what to do.