I believe they were removed if you didn't acquire them pre 4.0. As per the patch notes:
http://www.swtor.com/patchnotes/10202015/game-update-4.0-knights-fallen-empire-early-access
If you had it, it was moved to an archive section for you to use, but if you didn't earn it, it's no longer obtainable.
That would be so stupid, if it actually turns out to be true, because aside from people who were lucky enough to get the blue prints before 4.0, that would mean the only source of expertise crystals other than the black core ones would be the cartell market. PvP weapons come without colour crystals after all. Makes one wonder, just what Bioware/EA are thinking.
There is hope however:
My other lvl 50 crystals, that also weren't part of KotFE were not moved to the "Archives". The blue prints for those are also still available. All that is needed is some definite answers. I don't expect an official answer by the devs, though that would certainly help.
