Plants look ok.

Hammerhead is advanced nutrients tweak of the more common blooming additive, pk 13/14 and should be used only in the flowering stage. If it is as concentrated as canna's pk 13/14 it could well be the cause of your little problem there. Maybe burning them a bit? Not sure about holes in the leaves but possible i guess. Flush like cannakeeper says and have a look at the A/N site about the hammerhead.

Subzero :thumbsup: