If you think one strobe is not recycling as quickly as the other it should be easy to check. Set up everything inside the house, bend both strobes close to each other so you can see the ready lights, set them both to the same power level and take a picture (or three). Watch the ready lights and you'll have a better idea of what is going on.
If, in fact, one of the strobes is coming ready slower than the other, power off both strobes, switch the batteries, and try again. Either the problem will stay with a flaky strobe or it will follow the battery pack.
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