Give them another week before you try it. If you do want to add more carbonation, use drops, as any attempt to use corn sugar or any other granular primer will result in major foaming.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk