Is it possible to remove streaks that formed in cured epoxy?

Yes, it's possible to remove streaks from a cured epoxy surface, depending on how the streaks formed. If the surface is fairly smooth and the streaks are due to contamination, sand the surface lightly, remove residue, wipe the surface with denatured alcohol, allow to dry, and apply a flood coat of mixed epoxy. This is also the method to use to fix surface streaks that can happen if you suspect the epoxy resin and hardener were not mixed thoroughly enough.

If you have a swirly, streaky texture on the surface, sand or grind down the steaky texture until smooth, remove residue, wipe the surface with denatured alcohol, allow to dry, and apply a flood coat of mixed epoxy.