When you say "pulled up",do you mean that literally?.Its usually best,to go down with your hands,and feel if there are any first,and then if there are still some tiny ones attached,they will develop later.You can take the whole plant out carefully to look too,if you prefer,take off what you want,and put the plant back,to grow on..Did you earth them up and water well,as they grow above the tuber.I may have misread your question,so hope you do get a better result.