Have you really measured all your bridle lines, and flying lines, 4 years ago when you bought it, since you can compare?
Or have you got the original measurements on the bridles from North?
I would not put anything into this though...
How many other kites do you have - are they flying with the same trim on the same bar, just not the Evo?
Anyways, in general, over time your frontlines and bridles will slightly stretch (actually not shrink as much) so all kites begins to backstall a bit more over the years.
When reaching a certain point, it might feel like it comes "all of a sudden", eventhough a gradual change.
I would just either lengthen my rear lines a tad at the leader lines, or shorten the fronts - or add a bit longer pigtails on the Evo rear attachments, and you are just fine again
You can not measure kite bar lines to say they are "perfectly tuned" - no such thing exist....
Everything should fit as a complete setup, and this will never require the same bar trim for all kites