Did you include the Feb 2018 payment on your 2017 return as a payment? How did you pay it in Feb? Did you pay it online at the IRS or send in a check? If you sent a check did you use a 1040ES 2017 slip or a payment with an 2017 extension? You always include an estimated payment on the return it was for (not the year it was paid).
But the 4th quarter 1040ES payment is always due Jan 15. So I don't know if you paid in Feb right. You may have actually paid a 2018 1st quarter estimated payment.
