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Here I am more concerned that the drop of my credit score coincided with my unusual increase in debt. I was sure that in case of paying the debt off it does not affect the credit score. And now I think - maybe banks send information about the debt to the Bureau not only after, but also in the middle of the billing cycle? Nothing else but an increase in debt in the middle of the billing cycle did not happen.
Taking a CC to high utilization mid-cycle will not and cannot impact your FICO scores unless your lender does an off-cycle reporting and that higher current balance is reported. If you look at your CR, you'll see what your current reported balance is. If on your Citi card it still reads 4% or so from your last statement balance reporting, your score dropped 8 points for a reason other than your Citi card utilization. If higher balance was reported and is visibile on your CR, it's possible that the new balance was responsible for your score drop.
Bottom line is that it's what's on your CR (reported) that matters. Simply look at your CR and see what balance is reported for that account.
BrutalBodyShots, thank you very much!