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I'd be less concerned about the score differences, and more concerned about getting PFDs on those two collections.
Doing that would likely net a nice increase for you across all three.
What's your end goal? Why is the fixing the difference so important to you?
As for getting to the 700s ... what's the rest of your story? Do you have credit cards? Installment loans? Three revolvers and an installment loan help raise scores as you make payments on time, keep the UTI low and let them age.
At this point time and patience may be your best advice, unless you don't have cards or loans
Sorry, I overlooked your secured card comment.
A small secured loan will put an installment loan on your reports ... and provide another positive tradeline. You may also want to try to get a store card like Overstock. I got one with the shopping cart trick long before my scores were in the neighborhood of yours. Two secured bank cards and a store card is a good start.