You can prune them all now if you want to or wait until after they bloom.

If they have only one or two stems I would prune them now. You may not have bloom this year or the bloom may be late but pruning will encourage more stems to grow from the roots and you will have a stronger plant. If there are buds on the vine you can wait until after they bloom and then prune. But don't wait all summer.

Newly planted clematis are hard pruned in the spring for the first year or two regardless of their pruning group. For the same reason as above, to encourage good root growth and more stems. After that you can prune according to the pruning group for each plant or continue to prune all as type 3. Some people prune 2s as type 3s. They sacrifice the early bloom on the type 2s for the convenience of treating them all the same.

If you cut them back, don't forget to fertilize.