Can your Dahlias stand up by themselves?
These plants make a great flower, no doubt, but these plants will not stand up on their own. I gave them a pass last year, since they came from bare tubers, but after overwintering I was expecting stronger, self-sufficient plants. There's 3 of them, 2 of which get sun until about 2 pm, the other until about 1. Maybe that's not enough? Maybe a "normal" winter will kill them anyway?