I went through this when I lowered my 1.5", I added a BMR adjustable Panhard bar to correct the rear end shift.

I also found after a few thousand miles my tires were wearing slightly on the inside so I had to install MM Caster Camber plates to correct the front end alignment.

Then I discovered my pinion angle was off too, so I installed BMR adjustable upper and lower control arms. (you really only need one or the other).

If done properly lowering a car, as I found out the hard way, involves a lot more than just springs.

 

Are the springs properly seated in the bottom of the Strut (shock) where there is a "stop" for the end of the coil? If that got messed up during the assembly it will indeed change the ride height a bit.