Ideally, you want between 1 and 9 percent util on your CCs. Thing is, your next months minimum is going to probably put down to 0 percent util. So, to maintain this, you need to use the cards at least a little each month, and then mostly PIF when the bill comes. Your FICO scores should climb if you that small balance ride.
AMEX tends to be very generous with CLIs. It sounds like you're doing a good job managing your CCs. You're using them and you PIF each month. Getting more available credit will help your score, although initially most new accounts and inquiries create a small ding.
Getting rid of negatives and building up positives is the key to raising your score.
