You could try swapping them about - and see if that helps. I'm sure you have read in the past of my 'diy' balance system - and it's worked well for me. But it doesn't balance out any side to side unbalance on the wheel - ie it could be heavy on the outside rim at one point, and heavy on the inside rim at another point - possibly even at 180 degrees from the first. To get rid of this imbalance requires a proper 'dynamic' balance - rather than my crude 'static' method.
Do grages still do that - balance on the car ? My DIY stsic balance is 'on the car' and therefore takes the unbalanced brake drum into account (even more important with nice BIG brake drums!) - but doesn't consider the dynamic balance . I suppose with discs fitted - there is much less in the rotating assembly to be out of balance. The diy balance can still be used - just take the pads out to let the wheel swing free.
When you try swapping teh wheels & looking for missing balance weights give them a wire brishing inside too - surprising what a chunk of dried out mud can do to the balancing.
