The difference in speed is not a big issue, but I was throwing it out there to see if there were an easy fix.
Yes there is a fix and sort of easy. Either find another resistor that is closer to a perfect match to one of the two you have.
Tho sort of a pain in the bum if you have to sort threw and test a whole bunch of resisters till you find one thats just right.
being they can all vary by as much as 2-5%
Or you can also put a micro trim pot inline with one of the resistors (or both if you want) and then you can use the trim pot to fine tune the one that has less resistance till you have the exact same resistance on both sides.
Tho If the trim pots have the right Ohm values that you need you can even just skip the fixed value resisters and just use 2 mini trim pots. and dial them in till they match. You can also change the speed within a range of the trim pots ohm values that way to.