I'm just a little confused as it was when I watered it more heavily was when the issue began. Are you sure it requires more water?

From googling it mostly seems to match up with images of overwatered plants. I would need to be sure before watering it more as I wouldn't want to make the issue worse!

I have several bamboos in large pots/planters and when the leaves curl like that it means they need water. Usually after I water when they look like this, the leaves will begin to uncurl in a matter of minutes. I'm thinking it's rootbound and cannot retain water. Just my opinion by I am by no means an expert =/

Looks like not enough water. On days like you describe, I put the plant in a dish of standing water, that way it always has water available, and yet the roots aren't over saturated to the point where they get waterlogged and do the plant damage. That soil looks porous enough that I don't think you can over water it.

Bamboo leaves look like that when they don't have enough water. You can only overwater bamboo if its root mass sits under water for a couple of weeks. I think you have a problem because: 1) the plant is rootbound, so there is little soil to retain water, and 2) the leaves are getting desiccated because of the wind. You should repot that plant in a pot with at least twice the volume, keep it well watered, and give it a couple of months to recover.