I have a Rudbeckia planted in a container that has one thick and healthy stem, but the rest of the stems look thin and unhealthy. What is the best strategy here to encourage the growth of thick stems? In the photo, the stem on the right side is the thick one. To the immediate left of that is a slightly smaller new stem. Everything to the left of that looks beat up, thin, and not very strong or healthy.

I am in Zone 9b and the plant has put up an occasional flower all Winter long. I really want this plant to come in strong in Spring.

I could start using a fertilizer like MORBLOOM that is 0-10-10 to emphasize root growth.

I was thinking I could just cut all stems that are not healthy down to the base, and let the plant invest what energy it has into new stem growth.