All that happened was that you lost the FICO scoring bonus for having an installment account in your credit mix. While your balance was reporting less than 8.9% or the original loan balance you received an additional bonus. No worries, Amex understands these drops.
If anything, your payoff may be seen as a net positive because you reduced your debt-to-income ratio. A low or lowered DTI generally yields good results in the credit world and Amex takes DTI seriously. Don't worry.
As the other said, Op you are doing the right thing paying on your bills. Don't let the Fico scoring system make you feel down about your good habits. Amex would understand. When you lose a decent amount of points due to negatives showing up is when to be concerned.
