My seedlings died

I had very few seeds germinate and the couple that did, were spindley and fell over and died when they were about 3 inches tall. My other sunflowers (purchased from a garden centre) on the other side of the yard are about 8 inches tall and doing very well. I wonder if it was the elements. These seeds were planted in a less protected area.

Is it too late to try again? If it's possible to get the seeds in the ground and get them to grow, I would love to try again in a different location. We are in SW Ontario.

I have seen a couple HUGE roundish yellow and black bees, they almost look furry. Anybody know what these ones might be?