Okay I figured out what I was doing dumb:
I had created new textures (i.e. myTexture@x1 and myTexture@x2) but had mistakenly thought I needed to drag those into the tk2d sprite editor window and commit to rebuild-- so I was making entirely new sprites, not new platform sprites.
A followup question: What is best practice for file management if I'm starting with 4x textures?
ie-- my workflow is:
1) got all my tk2d sprites and sprite animators working fine with large textures just called "myTexture"
2) now I realize I need other platforms-- specifically 1x and 2x
3) i've added @1x and @2x textures to the same folder as myTexture so that the folder now has:
myTexture
myTexture@1x
myTexture@2x
4) I'm assuming since in tk2d editor I'm setting the 'current' platform to 4x, that I need an @4x in there somewhere. So is the proper workflow:
A) duplicate the myTexture so the folder has 4 items (myTexture, myTexture@4x, myTexture@2x, myTexture@1x)
or
B) just rename the original texture so the folder has 3 items (myTexture@4x, myTexture@2x, myTexture@1x)
Thanks for your help!!
Sebastian