I see three options.
1) if the gap is only 1/8" you might just leave it alone
2) you can cut out the scarf tenons and replace with spline pieces
3) you can increase the size of the holes. I think if I was to do this I would elongate the existing 1" diameter holes by just a little bit more than your 1/8" gap. You won't lose any relish on your tenons beyond the 1/8" mistake you now have. You will need to make custom shaped pegs. And you can still get the joint to draw up tightly.
To visualize this just draw two overlapping 1" circles whose centers are offset by 1/8" to represent the situation you now have. If each hole was elongated 1/8" in the proper direction you would have a regular fit. If each hole was elongated by a little more than 1/8" in the proper direction then you would get a drawbored fit.
Hope this helps. Good Luck.
--Chip
