Severe Leaf Cupping?

Hey guys,
I'm having an issue with the majority of my grow.
A lot of the leafs along the buds are cupping.

The grow medium is foxfarms organic & natural soil,
We've used Age old bloom, miracle grow, and super tea(bat guana and sea kelp) during flowering, the plants are set up in various weeks of flowering.
Flushed every 2 weeks, watered every 2-3 days, depending on if they need it.

I also have been adding sucanat in with the water each time I've watered, I've assumed this is the problem, so I've stopped this, but the leaves aren't getting any better.

Sorry for bad picture, I can take a better if needed.

what are your temps like..?

Mid seventies. Maybe a drop to mid sixties at night.

Here's a picture of a single leaf showing the extent of the curling on a lot of the leafs coming out of the cola's.