I've noticed plants droop a lot both from over and under watering.
The questions i always ask myself are: how long has it been since i watered.
how big is my container
Does it feel light when i pick it up
If i poke a hole an inch or two deep is the soil moist
I wouldn't trust me on the copper/ zinc because i'm just going off a chart, but it looks a lot like that to me. It could also be very early potassium (which sounds a lot more plausible since zinc and copper are pretty obscure nutrients) but theres no yellowing so I'm not sure.
You are getting around the time that potassium does start to matter but i don't really know whats in canna nutes so i could be way off.
Hope that helps.