I caved in! Returned the container to its old part shade spot, one of the leaves seems going lanky ready to flop, so I gave it a sip of water too. Seems the ones with more white colors are able to take the direct sun, but the ones with more green hates it...okay back to part shade. Then, I placed the slowest not performing container into the direct sun area, maybe it needs more heat at soil level to awaken the tubers.
