Asparagus crowns are a single plant. They do not branch out and make more. The roots get bigger each year and the shoots get bigger each year for several years then it levels off.

It sounds like a couple of your crowns died. Every year you can harvest the shoots for about a month then you must fertilize it and let it grow up big and do not cut it down until frost. It needs that time to make food and store it in the roots for next years crop. Mulch it over winter.

I have been planting asparagus for quite a few years. I put in a few crowns just about every year. If you want enough to make a good batch of spears, you need at least 25 crowns. More is better. I think I have around 40 crowns now and 10 of those are not old enough to harvest this year. I just planted 25 crowns this spring. Maybe in a couple of years we will be loaded with asparagus. As is we have been getting 1.5 pounds every two days for nearly a month now. Its about time for me to let it grow up.

I have one batch that became shaded with the orchard trees and it does not do so well in the shady conditions. It is surviving, but it is two weeks later coming up and doesn't produce like that in the sun. It helps if you can keep the weeds and grass out of the bed too.