I'd tackle the two biggest contributing factors to the score:
- Payment history
- Amount owed
So, one isn't an immediate fix, but hey, keep making your monthly payments on time. Never not making monthly payments on time. That's essential.
The other requires having the free cash flow to do it, but hey, if you can, reduce your credit utilization, i.e. start aggressively paying your debt down. The less credit utilization you have (~10 - 15% seems optimal from what I can tell), the better off you'll be. This seems like the faster of the two fixes, so if you're in the position to make it happen, well, give it a go!
Lemme know if #2 works (it'll probably take two months to reflect tho)!