No, it's not too late. They're even frost tolerant and shall hang in there until a hard freeze. To keep baskets in bloom all the time, it's helpful to just cut back half the stems at a time, and do it on an on-going basis, so it won't be that noticeable, but since you haven't pruned them at all yet, you may as well just do it all. How far depends on how long and straggly they are. Prolly at least by half.

I cut mine back to where they're only a few inches long and fertilize.

Deanna