Ray,
I'll bet you're right handed!
The line set was probably made without being adequately pre-stretched and you're seeing the results. Because your right hand/arm is stronger than your left, you're pulling harder and stretching the right line more than the left. Before you even up the lines, you might try stretching both lines evenly to about half of breaking strength. Then switch the lines right-to-left and fly for a session or two. Then compare the lengths ... they should be closer than the eight inches you have right now. Now adjust the lines to equalize them.
When new, spectra line will creep about 2 to 3% until it takes a set ... that's 20 to 30 inches for a 90 foot line set. On quad kites it's the top lines that stretch the most because they take more of a load than the bottom lines. Thus, most fliers rotate the top and bottom lines for the first few flights. Hardly anyone bothers with keeping left and right the same on quads, so that gets evened out without anyone the wiser. With dual line kites, you should rotate the left and right hand lines during the first dozen or so flights to even out the creep.
Even if you even out the lines right now, you should still rotate them to even out the creep. That will help to keep them even over time.
Cheers,
Tom