if the car sits lower with the new springs, then this is to be expected.

as the car rolls when making a turn, the outer suspension compresses, and the toe-link arm is there to toe-in the outer rear wheel, to prevent oversteer.

but also remember that the front track is slightly wider than the rear, so this could also be giving you an illusion of exaggerated rear toe-in (i.e., more than what is really there)