Can drying out late in flowering hurt my plants?

Letting a pot get properly dry between waterings is normal and healthy. Letting plants droop and wilt over and over is something else, and it is a myth that deliberate drought improves anything. Dry runs also concentrate salts around the roots.

Water to a steady rhythm and lift the pot to judge weight. A watering setup makes this easier, and a flush product like Canna Flush is meant for the last one to two weeks, following the label.