Discover 13,400 balance/14,000 credit limit

Target MasterCard 12,430 balance/12,800 limit

Jcpenney MasterCard 4,500 balance/5,500 limit

Home Depot 3,500 balance/21,000 limit

I have a 720 FICO. I've worked really hard to never be late. Sold an asset and now have $12,000 to pay down debt. What will give me the biggest bump in my score? I am hoping to refinance my mortgage.