For plant grooming advice see the link below.
Additional ties may be necessary. as the plants have gotten taller, to hold the plant up during a storm or heavy wind. Even a stem that looks strong and healthy may succumb as dahlia stems are often brittle.
Critters and fungi: This is a touchy subject. The big three in my area are red spider mites, broad/cyclamen mites and mildew. If left untreated they can damage a plant, or at least its attractiveness. The biological, organic, and chemical remedies are endless. The degree of intervention depends on how obsessive you are about having picture-perfect plants and blooms. I make no recommendations, because it is a matter of horticultural conscience.
As we move into August, enjoy your garden and be sure to groom the plants.
Good gardening,
Harry Rissetto