The sprouts are coming from rhizomes, normal growth habit for Rudbeckia fulgida. You could uncover gently some soil from one of them to see.

straight down pix are bad enough.. but upside down is something else.. lol .. wonder whats going on with houzz today with all the upside down pix ...

anyway ...if you want to know whats going on.. then dig them up and look.. and then replant it ...spring is the perfect time of year for such ...

and if you want a new clump somewhere else.. break a piece off and move it ..

most of us.. didnt have the WWW to rely on.. and to make us worry .. we just dug things up.. and learned.. and maybe killed a few things ...

btw: zone alone means nothing but min winter temp for one minute in the dead of winter.. big city location tells us much more.. but in this case.. the pic tells us.. its just coming out of dormancy ... so its planting time .. digging it up and replanting it would be no different that buying a new plant.. bare rooting it. and planting it ...

ken

ps: i would NOT dig things up in july and august .. not the right time of year ... i had to kill a few plants to learn that lesson ... lol ...