It is preferable to wait a few minutes in between attempts at a hefsek taharah. Waiting, possibly more than a few minutes, allows for natural lubrication to return, which can prevent irritation from the bedikah. It also gives a more accurate sense of whether the woman has in fact ceased bleeding. With ten minutes to sunset, it would have been desirable to wait more than a minute before trying another hefsek.

Even so, your second bedikah does count as a hefsek taharah, since it did show that bleeding was not ongoing at that very moment prior to sunset. You may continue to count your clean days.