We know that when the bohrok awoke, the Bahrag produced the krana to control the Bohrok. So when more krana were needed, the bahrag would give them to the Bohrok Va and they would take them to the Bohrok that needed krana. But now the Bahrag are locked away so where are the Krana Kal coming from. The Bohrok Va are serving the Bohrok Kal and carrying their krana so where did the Bohrok Va get the Krana Kal?

Maybe they were created from the original Krana just as the Bohrok Kal were created from the original Bohrok.

Possibly, seeing as the Krana-Kal are metallic Krana, the Krana-Kal are being formed from the protodermis, either that or the Va are forming them from the proto.

The Krana Kal are just Protodermis-Krana. Just like those yummy new ice creams Street are just starting to make, that are vannilla dipped in chocolate! (YUM!!) Anyway, the Bahrag probably put aside some Krana Kal w/ the B/Kal before they were captured.