Paying c/c accounts to $0 will generally lower your scores. It's always better to strategically charge and pay down to try and keep a small balance of (approx 7-9% utilization) unless your DTI is a concern. With a 620, you should be good to go now.
Best wishes to you!
Remember these thresholds: 8.9%, 28.9%, 48.9%, 68.9%, 88.9%
If you're not crossing a threshold, you won't be getting points.
Mortgage scores don't like more than one revolving credit card with a balance.
Get your CC aggregate utility at or below 8.9%. Look into the AZEO All Zero Except One technique for full FICO points optimization.
How many open installment loans do you current have? What is the utilization %?
Open installment loan similar to revolving CC react the same. You want to keep one open installment loan with utilization at 8.9% or less. Once you close all your installment loans, you'll lose those bonus points.
You might want to address any derogatory you have; delinquency, charge off, collection, etc. If they are updating monthly, it'll keep your scores suppressed.