How hot has it been? Sometimes a plant just can't keep up with the uptake of water no matter how much is in the soil.

tj

It has been reasonably cool this past week, 70's, raining and overcast. This coming week however, it's going to be sweltering hot! 90-100 all week and humid. This plant has done this every year I've had it, I'm wondering if it's 'normal' for this plant. It's quite concerning.

No, it's not normal. Mine only do that if I haven't watered in a couple of weeks...in the summer, with no rain, in clay soil, in Alabama.

I have seen Cone Flowers react that way if the soil is too saturated with water as well as if the soil lacks adequate moisture levels. In my very well drained sand here they tend to do that only when the soil gets water saturated.