I grabbed one of the blades to look into sharpening them and remembered the two outside ones had a piece of inner tube between them and the spindle. Just thought it was used to space the blades down, but found out why. The center bushing protrudes about .06 through the blade.
Here's the other side.
And a shot with the tube remains.
So I either need to find some thicker washers for the bolt head side or 'shave' the bushings. The bushings are 7/8" going through the blade. Could be someone bought some cheaper blades and they were just a bit thinner than originals. The blades don't look to have been sharpened.