18' Tacoma front lifted/stock rear now feels soft-

I've lifted the front end of my new 2018 TRD OFF-Road 4x4 using Billie's 5100's set at 0 and added OME 885's springs and the truck feels great until I hit a speed bump or smash through a dip at 20-30mph the stock rear end is a little spongee feel and really soft now compared to the front end.At time it almost feels like the its gonna come up off the ground. I'd like to maintain the ride height in the rear but maybe get something added back there that's gonna help the truck feel more planted without adding any lift. Help and suggestions is what I'm looking for.

Also with this added lift of about 2" in the front, is the diff spacer something that I should be looking at adding to avoid future issues, as I didn't get under the truck before it was lifted to notice a difference to the angles of driveshaft, 300 miles in and it was in the lift shop .Thanks.

 

Maybe a set of 5100’s for the rear now too?

 

You’re probably 1” higher in front, as well. I’d get 5100s for the rear and an AAL.